Pierre Boisaubert

Nasreddine Kébir
email: nasreddine.kebir@insa-rouen.fr

Anne-Sophie Schuller

Fabrice Burel

Photo-crosslinked coatings from an acrylate terminated non-isocyanate polyurethane (NIPU) and reactive diluent

Keywords: Polyurethane, non-isocyanate, NIPU, transurethanization, coating, acrylates, UV-Curing, reactive diluent

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Polyurethanes (PUs) are a class of very important polymer materials possessing versatile properties allowing them to be used in various application fields. Polyurethane acrylate systems (PUAs) are based on acrylate-terminated prepolymers that are crosslinked to afford protective coatings displaying very good abrasion and chemical resistances and very flexible mechanical properties. [START_REF] Decker | Polymérisation sous rayonnement UV[END_REF][START_REF] Fu | Research progress of UV-curable polyurethane acrylate-based hardening coatings[END_REF] The attention towards UV-curable coatings is continually increasing owing to their fast curing and low energy consumption. [START_REF] Seo | Preparation and properties of poly(urethane acrylate) films for ultraviolet-curable coatings[END_REF] Their formulations are usually composed of three major components: photoinitiator, reactive oligomer and reactive diluent. [START_REF] He | UV-curable hybrid coatings based on vinylfunctionlized siloxane oligomer and acrylated polyester[END_REF] The reactive diluent decreases the viscosity of the formulation and copolymerizes with the oligomer. The chemical structure of the oligomer defines the viscoelastic properties of the final crosslinked material. [START_REF] Fouassier | Photoinitiators for Free Radical Polymerization Reactions[END_REF] Epoxy acrylate, polyester acrylate and urethane acrylate oligomers (PUAs) are commonly used in the preparation of free radical UV-curable coatings. [START_REF] Khudyakov | Structure-property relations in UVcurable urethane acrylate oligomers[END_REF] PUAs are conventionally prepared by acrylation of telechelic polyurethane oligomers, synthesized by the conventional reaction between polyols and toxic diisocyanates, which are obtained from diamines and toxic phosgene. [START_REF] Maurya | A Review on Acrylate-Terminated Urethane Oligomers and Polymers: Synthesis and Applications[END_REF] During the two last decades, some research groups have proposed alternatives to prepare PUA materials by non-isocyanate and non-phosgene routes (NIPUAs). [START_REF] Assumption | Photopolymerization of urethane dimethacrylates synthesized via a non-isocyanate route[END_REF][START_REF] Figovsky | Foamable photo-polymerized composition[END_REF][START_REF] Huang | Synthesis and properties of UV-curable tung oil based resins via modification of Diels-Alder reaction, nonisocyanate polyurethane and acrylates[END_REF][START_REF] Hwang | Functional polyurethane prepolymer, method of preparing polyurethane by using the same, and application method thereof[END_REF][START_REF] Monnier | Oligomères uréthane acrylates mono ou multifonctionnels sans isocyanate[END_REF][START_REF] Monnier | Oligomère uréthane acrylé ou méthacrylé sans isocyanate[END_REF][START_REF] Hwang | A new UV-curable PU resin obtained through a nonisocyanate process and used as a hydrophilic textile treatment[END_REF][START_REF] Wang | Investigation of non-isocyanate urethane dimethacrylate reactive diluents for UV-curable polyurethane coatings[END_REF][START_REF] Figovsky | Foamable photo-polymerized composition[END_REF][START_REF] Figovsky | Foamable photo-polymerized composition[END_REF][18] Recently, the photo-curing of poly(hydroxyurethane) acrylate (PHU) oligomers, obtained by the polyaddition of cyclic dicarbonate with diamine monomers followed by acrylation have been studied. [START_REF] Monnier | Oligomères uréthane acrylates mono ou multifonctionnels sans isocyanate[END_REF][START_REF] Monnier | Oligomère uréthane acrylé ou méthacrylé sans isocyanate[END_REF][START_REF] Figovsky | Foamable photo-polymerized composition[END_REF]18 However, as far as we know, the photo-crosslinking of NIPUA oligomers obtained by the transurethane polycondensation, which is one of the most promising free isocyanate pathways to polyurethanes, has not yet been described. [START_REF] Unverferth | Renewable non-isocyanate based thermoplastic polyurethanes via polycondensation of dimethyl carbamate monomers with diols[END_REF][START_REF] Duval | Synthesis and properties of renewable nonisocyanate polyurethanes (NIPUs) from dimethylcarbonate[END_REF][START_REF] Martin | Synthesis and properties of allyl terminated renewable non-isocyanate polyurethanes (NIPUs) and polyureas (NIPUreas) and study of their photo-crosslinking[END_REF][START_REF] Kébir | Nonisocyanate thermoplastic polyurethane elastomers based on poly(ethylene glycol) prepared through the transurethanization approach[END_REF][START_REF] Kebir | Non-Isocyanate Thermoplastic Polyureas (NIPUreas) through a methyl carbamate metathesis polymerization[END_REF][START_REF] Kebir | Elaboration of AA-BB and AB-type Non-Isocyanate Polyurethanes (NIPUs) using a cross metathesis polymerization between methyl carbamate and methyl carbonate groups[END_REF][START_REF] Li | Synthesis and properties of non-isocyanate aliphatic crystallizable thermoplastic poly(ether urethane) elastomers[END_REF] This pathway consists in the reaction of dialkyl dicarbamates [START_REF] Unverferth | Renewable non-isocyanate based thermoplastic polyurethanes via polycondensation of dimethyl carbamate monomers with diols[END_REF][START_REF] Duval | Synthesis and properties of renewable nonisocyanate polyurethanes (NIPUs) from dimethylcarbonate[END_REF][START_REF] Martin | Synthesis and properties of allyl terminated renewable non-isocyanate polyurethanes (NIPUs) and polyureas (NIPUreas) and study of their photo-crosslinking[END_REF][START_REF] Kébir | Nonisocyanate thermoplastic polyurethane elastomers based on poly(ethylene glycol) prepared through the transurethanization approach[END_REF] or dihydroxyethyl dicarbamates 23- 25 with diols, in presence of organic or organo-metallic catalysts. However, with dihydroxyethyl dicarbamates, a weak proportion of urea functions are formed owing to a back-biting side reaction. [START_REF] Kebir | Non-Isocyanate Thermoplastic Polyureas (NIPUreas) through a methyl carbamate metathesis polymerization[END_REF][START_REF] Kebir | Elaboration of AA-BB and AB-type Non-Isocyanate Polyurethanes (NIPUs) using a cross metathesis polymerization between methyl carbamate and methyl carbonate groups[END_REF][START_REF] Li | Synthesis and properties of non-isocyanate aliphatic crystallizable thermoplastic poly(ether urethane) elastomers[END_REF] On the other hand, the transurethane polycondensation gives conventional PU structures and not poly(hydroxyurethane) structures (PHUs). [START_REF] Shen | A comparison of non-isocyanate and HDI-based poly(ether urethane): Structure and properties[END_REF][START_REF] Li | Synthesis and characterization of aliphatic thermoplastic poly(ether urethane) elastomers through a non-isocyanate route[END_REF][START_REF] Cornille | A perspective approach to sustainable routes for non-isocyanate polyurethanes[END_REF] In this work, we describe the preparation of UV-curable coatings from several urethane and non-urethane reactive diluents and a NIPU-acrylate oligomer (NIPUA), obtained by the transurethane polycondensation approach. The impact of the reactive diluent chemical structure and content on the mechanical and thermal properties of the resulting coatings is investigated.

EXPERIMENTAL

Materials

Poly(tetramethylene oxide) (PTMO) of = 2000 g/mol, 1,6-diaminohexane (98%), 1,5,7triazabicyclo[4.4.0]dec-5-ene (TBD, 98%), dimethyl carbonate (DMC, 99%, anhydrous), ethylene carbonate (99%, anhydrous), were obtained from Sigma Aldrich. Acryloyl chloride (96%), 4methoxyphenol (MeHQ, 99%) and triethylamine (99%) were supplied by Fisher Scientific. Diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure 819) and Ethyl phenyl(2,4,6trimethylbenzoyl) phosphinate were supplied by BASF. All the other reagents and solvents were used without further purification. The reactive diluents HDDA (hexamethylene diol di-acrylate) and UDMA (urethane diol di-methacrylate) were supplied by Esstech.

Synthesis

Preparation of Dimethylhexane-1,6-dicarbamate (BMC-C6)

In a neat round bottom flask equipped with a magnetic stirrer, hexamethylenediamine (1 eq.), TBD (0.1 eq.) and DMC (10 eq.) were added and stirred for 5 h at 80 °C. Then, the reaction medium was cooled to room temperature. Crystallized product (BMC-C6) was recovered by filtration (yield > 85 %) and washed by distilled water to remove TBD. 1 H NMR (300 MHz, CDCl3, δ): 4.67 (s, broad, 2H; NH), 3.65 (s, 6H; NH(CO)OCH3), 3.15 (m, 4H; NHCH2); 1.48 (m, 4H; NHCH2CH2), 1.32 (m, 4H; NHCH2CH2CH2).

13

C NMR (75 MHz, CDCl3, δ): 26.2, 29.9, 40.7, 52.0, 157.1 ; IR (ATR): ν∼3300 cm -1 (m; νNH), ∼1700 (s, νCO H-bonded) cm -1 , ∼1530 cm -1 (s, νNH bending).

Preparation of hydroxy-terminated NIPU oligomer H-C6-2000

In a three-necked round-bottom flask equipped with a mechanical stirrer, a Dean Stark condenser and connected to a vacuum pump, BMC-C6, and poly(tetramethylene oxide) of Mn =2000 g/mol (PTMO 2000) were added at an appropriate molar ratio previously calculated by Carothers theory to reach the desired degree of polymerization. The temperature was progressively risen to 160 °C under nitrogen flow and stirring. Then, 10 mol% of MeOK catalyst in regard to BMC monomer was added. After 1 h of reaction at 160 °C, the reaction mixture was placed under vacuum (400 mbar, 1 h). Finally, the pressure was carefully reduced to 0.5 mbar during 4 h. After cooling down to room temperature under nitrogen flow, H-C6-2000 was recovered without any purification.

Preparation of Acrylate-terminated NIPU Oligomer A-C6-2000

H-C6-2000 was introduced in a neat round bottom flask equipped with a magnetic stirrer, under a nitrogen stream. The oligomer was solubilized in anhydrous DCM. Triethylamine (3.5 eq.), previously distilled under KOH pellets, was added to the reaction mixture. After cooling down the mixture to 0 °C using an ice bath, acryloyl chloride (3 eq.) was added dropwise into the reaction mixture. When addition was completed, the mixture was allowed to react during 6 h at room temperature. Filtration of triethylammonium salts was then carried out. After, mixture was washed three times by HCl (1M), NaOH (1M) and finally brine. First organic phase was recovered and the oligomer part remaining into the aqueous phase was extracted by DCM. Treatment was repeated and the organic phases were combined, dried over MgSO4, and filtrated. Around 300 ppm of 4-methoxyphenol stabilizer was added and solvent was evaporated. Finally, the obtained yellow product was dried using high vacuum at 25°C.

Preparation of the reactive diluent BHECA (Bis(HydroxyEthyl Carbamate Acrylate))

In a 250 mL 3-necked flask, 24.05 g (0.27 mol) ethylene carbonate and 15.05 g (0.13 mol) of 1,6hexanediamine were stirred in N2 atmosphere at 90 °C for 2 h. Then, the reaction temperature was increased to 120 °C during 5 h. After cooling to room temperature, the obtained white crude product was washed with 150 mL of water, was filtered, and was recrystallized in water (29.39 g, yield: 78 %). Then, this product (23.80 g, 0.08 mol, 1 eq.) was reacted with acryloyl chloride (16.93 g, 0.18 mol, 2.21 eq.), in presence of trimethylamine (19.77 g, 0.20 mol, 2.40 eq.), in DCM for 6h at room temperature. The obtained BHECA was a yellowish solid (yield: 60 %). Then, 5.0 g of BHECA was purified over a flash column, using a DCM/MeOH (97:3) mixture as eluent. A white powder was obtained (3.3 g, purification yield: 66 %).

Preparation of photo-crosslinked NIPU coatings (NIPUAs)

Formulations were prepared by dissolving A-C6-2000 and the reactive diluent in an appropriate amount of butyl acetate leading to a convenient viscosity. Then, 3.3 wt% of BAPO-TPOL photoinitiator (BAPO-TPOL) were added to the mixture. Formulations were stirred up to 2 hours in order to obtain homogeneous media. Then, the obtained formulations were casted to stiff matte steel "Q-panel" plates supplied by Labomat. After degreasing the plates with a cloth soaked in ethanol (EtOH), two types of coatings were prepared for each type of formulation, i.e. "thin" and "thick" films. In order to obtain thin films, the desired formulation was applied on the top of the plate and wet thickness control was provided using a roll coater. To obtain thick films, slides of an adhesive tape on the borders were used to calibrate the thickness. The plates were then put in a UV conveyor (UV Fusion Light Hammer 6) to perform photo-crosslinking of the NIPU coatings.

Measurements and Instrumentation

1 H and [START_REF] Monnier | Oligomère uréthane acrylé ou méthacrylé sans isocyanate[END_REF] C NMR analysis were performed on a Bruker 300 Fourier Transform spectrometer at 300 MHz and 75 MHz respectively, in CDCl3 solutions containing tetramethylsilane (TMS) as internal standard.

IR spectra were acquired with a FTIR (Perkin-Elmer Spectrum 2000 FTIR), provided with a diamond ATR device (Attenuated Total Reflection). Spectra were recorded from 10 scans in the 500 to 4000 cm -1 range.

Average molecular weights of polymers (Mn and Mw) and dispersity (Ð = Mw/Mn) were assessed by Size Exclusion Chromatography (SEC). Polymers were dissolved in dichloromethane, filtered (0.45 µm) and analyzed at 25°C by a Varian PL-GPC50 system provided with two mixed packed columns (PL gel mixed type C). Dichloromethane was used as the mobile phase and PMMA standards (from 875 to 680000 g mol -1 ) were used for calibration.

Thermo-Gravimetric Analysis (TGA) was achieved with a TGA Q500 device (TA Instruments), using a heating rate of 10°C/min under a nitrogen flow. The temperature at 5% of weight loss (T5%) was used as reference to estimate the degradation of polymers. Differential Scanning Calorimetry (DSC) was achieved with a DSC Q2000 device (TA Instruments), using a heating rate of 10°C/min under a nitrogen flow. The midpoint method was used to evaluate the glass transition temperature (Tg). Melting temperature (Tm) was measured at the maximum of the endothermic signal. DSC curves were realized in a temperature range of -80 to 300°C.

The thickness of cross-linked thin films (<50 µm) was measured by magnetic determination using the PosiTector 6000, according to ISO 2808: 2007, with an accuracy of ± 1.0 micron. The device consists of a probe to be applied against the coating, previously deposited on a flat surface. The thickness of the thick crosslinked films (film thickness between 100 µm and 1 mm) was measured with a Digimatic micrometer, with an accuracy given to the nearest micrometer. The coating is clamped by a micrometer screw between the two circular measuring surfaces of the device.

The tensile analyses were performed on a Zwick/Roell device equipped with a 500 N force sensor, two jaws (pneumatic or manual clamping, depending on the type of sample characterized) and a movable crosshead. The tests were carried out in accordance with ISO 527_3 "Test conditions for films and foils". For each tested coating, between 5 and 15 rectangular specimens were cut out with a scalpel. Specimens with unevenness or notches were systematically removed. The manually clamped jaws limit the width of the specimens to 6 mm, the specimens have the following dimensions: a total length l3 of 50 mm; a width b of exactly 4 mm; a thickness h always less than 1 mm. The values of b and h were measured precisely at three points and the average of the three measurements were used for the calculations. The distance between jaws L0 was fixed at 35 millimetres. The test speed υ was fixed at 20 mm/min, and the preload value was maintained at 0.05 MPa. After each sample has been broken, the following values shall be determined as a function of the cross-section A (A = b × h, expressed in mm 2 ) of the sample: The breaking strength of the material σr (MPa) which corresponds to the stress experienced when the specimen breaks, often equal to the maximum stress; the elongation at break εr (%) which corresponds to the elongation of the material before it breaks; Young's modulus or Elasticity E (MPa) which corresponds to the slope of the stress/strain curve in the range between ε1 = 0.05% and ε2 = 0.25% of the elongation of the material considered reversible.

For swelling tests, mass (mi) samples of approximately 15 mg (thin films) and 50 mg (thick films) were placed in 4 mL pill dispensers containing 3.5 mL of THF and then placed under magnetic agitation at room temperature for 24 h. The samples were removed from the solvent, dried on the surface with absorbent paper and weighed (mh). These samples were then dried in a vacuum oven at 40°C for 24 h and weighed (mf).

-The extractables percentage (τEX) of the samples was expressed in % as follows: = mi -mf mi × 100 Eq.1

-The swelling (Q) of the samples was expressed in % as follows:

Q = mh mf mf × 100
Eq.2

RESULTS AND DISCUSSION

Synthesis and characterizations of acrylated NIPU oligomer

Dimethylhexane-1,6-dicarbamate (BMC-C6, Scheme 1), was prepared by a reaction of a large excess of dimethylcarbonate (DMC) (to avoid any cyclization or chain extension) with hexamethylene diamine, in the presence of TBD as catalyst, as previously described. [START_REF] Duval | Synthesis and properties of renewable nonisocyanate polyurethanes (NIPUs) from dimethylcarbonate[END_REF][START_REF] Martin | Synthesis and properties of allyl terminated renewable non-isocyanate polyurethanes (NIPUs) and polyureas (NIPUreas) and study of their photo-crosslinking[END_REF][START_REF] Kébir | Nonisocyanate thermoplastic polyurethane elastomers based on poly(ethylene glycol) prepared through the transurethanization approach[END_REF][START_REF] Kebir | Non-Isocyanate Thermoplastic Polyureas (NIPUreas) through a methyl carbamate metathesis polymerization[END_REF][START_REF] Kebir | Elaboration of AA-BB and AB-type Non-Isocyanate Polyurethanes (NIPUs) using a cross metathesis polymerization between methyl carbamate and methyl carbonate groups[END_REF] The mixture was allowed to react for 6h at 80°C. The solid monomer was then recovered by crystallization with yield higher than 90%. BMC-C6 can be considered as potentially biobased since hexamethylene diamine [31][32] and DMC [START_REF] Choi | Selective and high yield synthesis of dimethyl carbonate directly from carbon dioxide and methanol[END_REF][START_REF] Ballini | TBD-catalysed solventless synthesis of symmetrically N,N'-substituted ureas from primary amines and diethyl carbonate[END_REF] can be prepared from renewable feedstock. It also can be considered as potential substitute of hexamethylene diisocyanate. Scheme 1. Synthesis approach of acrylated NIPU oligomers.

NIPU oligomer with hydroxyl end-groups (H-C6-2000) was first prepared by a transurethane polycondensation reaction between BMC-C6 and an excess of poly(tetramethylene oxide) (PTMO, = 2000 g/mol) (Scheme 1). PTMO is an interesting polyol since it affords good resistance to hydrolysis and good mechanical characteristics to polyurethane materials. [START_REF] Suryawanshi | Advances in the synthesis of non-isocyanate polyurethanes[END_REF] The targeted of H-C6-2000 was 5500 g/mol. Thus, the targeted Xn was deduced from the following equation: Using Carothers' theory, 36 the degree of polymerization " " and the number of repeating units "n", can be written as follows: 37

= 1 + 1 + -2 = 2 + 1 Eq.4
Where is the stoichiometric ratio of reagents (r < 1), and is the conversion of the limiting reagent.

If we assume that p → 1, the stoichiometric excess of diols to be used « 1/ » can be calculated as follows:

1 = + 1 - 1
Eq.5

The hydroxy-terminated oligomer H-C6-2000 was reacted with acryloyl chloride to obtain the acrylate analogue A-C6-2000. The reaction was conducted in dichloromethane (DCM) at room temperature during 6h. Then, the organic phase was washed several times in acidic and basic aqueous solutions to eliminate by-products. Before evaporation of the organic phase, 300 ppm of methoxyphenol (MeHQ) were added to prevent cross-linking of the recovered product (yield: 76%).

The FTIR spectra (Figure 1) revealed the disappearance of the band at around 3500 cm -1 arising from stretching vibration of the terminal hydroxyl functions (H-O). We can also observe the C-H bending bands of the acrylate group at around 1410 cm -1 (in-plane) and 810 cm -1 (out-of-plane). The stretching vibration band of C=O of the ester-acrylate groups appeared at around 1725 cm -1 , and was overlapped with the C=O stretching vibration band of the free urethane groups (1720 cm -1 ). Other urethane bands are detected at 1686 cm -1 (H-bonded C=O, stretching) and 1526 cm -1 (N-H bending). The stretching vibration of N-H bonds of urethane groups appeared at around 3300 cm -1 . 1 H NMR spectra (Figure 2) revealed the shift of the signal "6" of the terminal methylene protons owing to the electron-withdrawal effect of the introduced acrylate groups from δ = 3.61 ppm ((t, CH2-OH) to approximately δ = 4.17 ppm (t, CH2-OCOR)). The new acrylate proton signals appeared at around δ = 6.39 ppm (signal "10", dd, R-OCOCH=CHtransH, [START_REF] Seo | Preparation and properties of poly(urethane acrylate) films for ultraviolet-curable coatings[END_REF] Jtrans = 17 Hz, 2J ≈ 1 Hz), δ = 6.11 ppm (signal "9", dd, R-OCOCH=CH2, [START_REF] Seo | Preparation and properties of poly(urethane acrylate) films for ultraviolet-curable coatings[END_REF] Jtrans = 17 Hz, 3 Jcis = 10 Hz) and δ = 5.81 ppm (signal "11", dd, R-OCOCH=CHcisH, 3 Jcis = 10 Hz, 2J ≈ 1 Hz). [START_REF] Monnier | Oligomère uréthane acrylé ou méthacrylé sans isocyanate[END_REF] C NMR spectra displayed the signals of the two acrylate carbons (δ = 130.5 and 128.6 ppm), as well as the quaternary carbon of the acrylate ester (δ = 166.3 ppm).

A-C6-2000 exhibited waxy solid aspect with Mn values of 5650 and 11100 g/mol by 1 H NMR and GPC, respectively. The dispersity determined by GPC was of 2.2.

The percentage of urethane groups and of hard segments within the acrylated oligomer were, respectively, calculated as follows:

% = [ !× × "#$%&'($ ( ] × 100 = 3.4%
Eq.6

%./ = [(( -2 × ) × )/ ] × 100 = 5.0% Eq.7

B A

Preparation and characterizations of photo-crosslinked coatings

NIPUA coatings were then prepared by photo-curing of the A-C6-2000 oligomer with different proportions of reactive diluents, which were used to reduce viscosity of formulations and tune the cross-linking density of the final coating and its properties. [START_REF] Decker | Polymérisation sous rayonnement UV[END_REF] Reactive diluents for free radical photocuring of coatings are usually acrylic or methacrylic monomers. [START_REF] Srivastava | UV curable polyurethane acrylate coatings for metal surfaces[END_REF] Generally, unlike multi-functional reactive diluents, mono-functional reactive diluents lead to decreased modulus and increased ductility. [START_REF] Srivastava | Analyzing monomer performance: the effect of difunctional reactive diluents on the properties of UV-curable polyurethane acrylates[END_REF] A high average functionality leads to high conversion and high crosslink density [START_REF] Young | Effect of comonomer concentration and functionality on photopolymerization rates, mechanical properties and heterogeneity of the polymer[END_REF] , increasing material hardness at the expense of flexibility. [START_REF] Decker | Photoinitiated curing of multifunctional monomers[END_REF][START_REF] Andrzejewska | Photopolymerization kinetics of multifunctional monomers[END_REF] However, a high functionality also can lead to low final conversion owing to gelation phenomenon. Three reactive diluents were chosen, i.e. HDDA (Hexamethylene Diol Di-Acrylate, Esstech), a commercial diluent widely used in industry; 7 UDMA (Urethane Diol di-MethAcrylate, Esstech) and BHECA (N-hexamethylene dihydroxyethyl carbamate diacrylate), a laboratory-prepared compound. Their chemical structures are shown in Scheme 2. Commercial diluents were liquids. UDMA was more viscous than HDDA. BHECA was a white solid obtained by aminolysis of ethylene carbonate by a default of hexanediamine, then functionalization of the resulting hydroxyl end groups by acryloyl chloride. Its structure has been evidenced by 1 H and [START_REF] Monnier | Oligomère uréthane acrylé ou méthacrylé sans isocyanate[END_REF] C NMR and FTIR (supporting data). Scheme 2. Photo-crosslinking approach of the A-Ol oligomers in presence of reactive diluent.

The formulations were prepared in butyl acetate (AcOBu) with a combination of two type I free-radical photoinitiators (TPO-L and BAPO, Scheme 2) at 3.3 wt.%. They were then photocrosslinked under a UV conveyor equipped with a parabolic mercury vapor lamp. For reproducibility, the light dose received by samples after one pass was adjusted to about 1.2 J/cm 2 (intensity of approx. 10 W/cm 2 in the UVA + UVB + UVC range, constant conveyor speed at 5 m/min. The coatings were prepared in two series of thicknesses, of approximately 30 µm (thin films) and 160 µm (thick films).

The weight percentage of HDDA was varied from 10 to 50 wt.% (NIPUA-H series). Because of the presence of two urethane functions, UDMA and BHECA were used at 20 wt.% but no more (NIPU-U20 and NIPU-B20) to get flexible materials. The obtained coatings exhibited yellowish, transparent, smooth and homogeneous physical appearance. Some pictures are available in the supporting data.

Conversions were calculated by FTIR in ATR mode by monitoring the band at σ = 1410 cm -1 arising from the C-H bending (in-plane) of the acrylate group. The conversion χ was calculated as follows:

1 = 2 3 2 4 5 - 2 5 3 2 5 4 5 2 3 2 4 5
× 100 Eq.8

Where 2 3 and 2 5 3 are the absorbance values of the band at 1410 cm -1 (δ(=C-H)) of the formulation at initial and final curing times, respectively. 1 Notation: H = HDDA, B = BHECA, U = UDMA. The numbers 10, 20, 30, 40 and 50 are the weight percentages of the reactive diluents within the coatings.

2 Double bond concentration of the « A-Ol + reactive diluent » systems. [START_REF] Seo | Preparation and properties of poly(urethane acrylate) films for ultraviolet-curable coatings[END_REF] Dry extract from AcOBu formulations (the weight percentage of non-volatile matter after solvent evaporation). [START_REF] He | UV-curable hybrid coatings based on vinylfunctionlized siloxane oligomer and acrylated polyester[END_REF] Conversion of acrylate double bonds estimated by FTIR. The conversion values (χ) of acrylate groups are displayed in Table 1. We can observe that conversion increased with the HDDA content within NIPUA-H series. Conversion in the case of the material based on UDMA was lower comparing to conversion of the NIPUA analogue based on BHECA. This may be explained by the lower reactivity of methacrylate comparing to acrylate groups. An increase of viscosity may also explain this limitation of conversion. Overall, the obtained conversion values are in consistency with those of PUAs systems. [START_REF] Decker | Polymérisation sous rayonnement UV[END_REF][START_REF] Fu | Research progress of UV-curable polyurethane acrylate-based hardening coatings[END_REF][START_REF] Llorente | Study of the crosslinking process of waterborne UV curable polyurethane acrylates[END_REF] The average molecular weights between crosslinked network's knots (acrylate functions) were calculated as follows: 6(7 7) = a×MNIPUA + b×Mreactive diluent Eq. 9

where a and b are the molar ratio of NIPUA and the reactive diluent (a+b=1).

The swelling tests were performed in THF as solvent, the values of the extractable ( 8 ) and swelling (Q) percentages are presented in Table 2. 8 values of NIPUA coatings are below 11 %, and most of them are below 6 %, suggesting that the obtained NIPUAs are well crosslinked. In addition, these coatings were chemically stable in THF. On the other hand, as expected, the swelling percentages of coatings were proportional to Mc(A-A) and ranged from 61 to 313%. Nevertheless, these values are higher in the case of thick films comparing to their thin analogues with roughly same extractible amount. This ambiguous phenomenon could be explained by geometric reasons of the samples.

Thermal properties

The thermal stability of coatings was assessed by TGA under nitrogen atmosphere. The temperatures at 5% of weight loss (T5%) are listed in Table 3, they ranged from 255 to 318°C showing a good thermal stability. Figures 4 and5 display typical TGA curves and their first derivative curves giving Tmax (temperature at maximum degradation rate) of each step. As for conventional polyurethanes, [START_REF] Assumption | Photopolymerization of urethane dimethacrylates synthesized via a non-isocyanate route[END_REF][START_REF] Llorente | Study of the crosslinking process of waterborne UV curable polyurethane acrylates[END_REF] thermal degradation of NIPUA coatings occurs in two-steps, with degradation of the hard segment parts (HS, Tmax ≈ 320 °C) followed by the PTMO soft segment parts (SS, Tmax ≈ 410 °C). The A-C6-2000 prepolymer revealed similar two-step degradation profiles. than NIPUA-H10 because of their quite similar crosslinking density (MA-A around 1800 g/mol). In addition, the glass transition temperatures of the soft segments were not observed at the screened temperature range (T > -60 °C). The literature value of Tg for PTMO2000 is -84°C. [START_REF] Vargo | A multitechnique surface analytical study of a segmented block copolymer poly(ether-urethane) modified through an H2O radio frequency glow discharge[END_REF] Increasing the crosslinking density with reactive diluents do not increase the value of Tg above -65°C, which suggests nanophase segregation implying limited HS -SS interactions. [START_REF] Barbeau | Morphological analysis of photocured polyurethane acrylate networks. Correlation with viscoelastic properties[END_REF] The DSC analysis also showed an exothermic phenomenon around 170°C for all the films with enthalpies ranging from 17 to 100 J/g (Table 3 and Figure 6). This phenomenon may also explain why the onset of degradation is observed before 200°C on the TGA curves. The residual photoinitiator underwent degradation around 170°C (Figure 5), which could lead to a restructuring/degradation of the network via chain breaks, restoring mobility to the soft segments, which could then reorganize. [START_REF] Maurya | A Review on Acrylate-Terminated Urethane Oligomers and Polymers: Synthesis and Applications[END_REF] This would explain the reappearance of the melting peak of the soft segments at the next heating (Figure 6).

Mechanical properties

The uniaxial tensile tests have been performed on thick NIPUAs films to assess their mechanical properties. The results are displayed in Table 4. Typical stress/strain curves are presented in Figures 7 and8. A large spectrum of properties was obtained by varying the amount and nature of the reactive diluent. Young modulus (strength properties) varied from 2.69 to 10 MPa, breaking stress (σr, strength properties) from 3.62 to 11.2 MPa, and elongation at break (εr, elasticity) from 64 to 470%.

The influence of the cross-linking density on the mechanical properties has been studied on coatings containing HDDA reactive diluent (NIPUA-H series). HDDA content has a considerable impact on the elastic behavior of the material. Indeed, elongation at break drops dramatically (from 470 to 140%) as soon as 10 wt.% of HDDA is added. Conversely, stiffness increases more linearly with the percentage of HDDA content, as shown by Young's modulus values (Table 4). overall mechanical properties of the materials (Figure 8). These improvements could be the result of the additional interaction provided by the H-bonds formed by the urethanes with the other compounds in the NIPUAs coatings. [START_REF] Wang | Investigation of non-isocyanate urethane dimethacrylate reactive diluents for UV-curable polyurethane coatings[END_REF] The branched structure of UDMA could promote miscibility between HS/SS phases while the symmetrical and linear structure of BHECA could promote phase segregation, which explain their different behavior in terms of elasticity (εr = 140 and 210 %, respectively).

CONCLUSIONS

A NIPU oligomer with acrylate chain-ends (A-Ol) was prepared by transurethane polycondensation reaction of an excess of PTMO2000 with hexamethylene dicarbamate, followed by reaction with acryloyl chloride. Eight NIPU acrylate coatings (NIPUAs) were prepared by photocrosslinking A-Ol in formulation with three reactive diluents under a high-intensity UV system. The reactive diluent content and chemical structures had a significant impact on the thermal and mechanical properties of NIPUAs coatings. The obtained properties were in consistency with those of the flexible PUs currently developed on the market (T5% > 255°C; E = 2.69 -25.5 MPa, σr = 3.62-11.8 MPa, εr = 56 -470 %). Finally, this work evidences the possibility to prepare polyurethane acrylate formulations without using isocyanates. In addition, the advantage of the developed system is that we can tune the length and chemical structure of the acrylate oligomer and reactive diluent as well as the crosslinking density, which offers us a wide range of possible properties.

  weight of PTMO. -= Molecular weight of BMC. -= Molecular weight of methanol.

Figure 1 :

 1 Figure 1: FTIR spectra of the oligomers H-C6-2000 and A-C6-2000.

Figure 2 : 1 H

 21 Figure 2: 1 H NMR spectra of H-C6-2000 (A) and A-C6-2000 oligomers (B).

2 4 5 and 2 5 4 5

 5 are the absorbance values of the C-H sp3 stretching bands.

  [START_REF] Fouassier | Photoinitiators for Free Radical Polymerization Reactions[END_REF] Y = Yellow, S = Soft, SR = Semi-rigid, F = Fragile, T = Transparent.

Figure 4 :

 4 Figure 4: TGA curves (solid curves) and their first derivatives (dashed curves) of A-C6-2000, NIPUA-H10, NIPUA-U20 and NIPUA-B20.

Figure 5 :

 5 Figure 5: TGA curves (solid curves) and their first derivatives (dashed curves) of A-C6-2000, NIPUA-H10, NIPUA-H30 and NIPUA-H50 as well as BAPO-TPOL photo-initiator.

Figure 6 :

 6 Figure 6: DSC curves of NIPUA-H0 to NIPUA-H50 coatings. 1 st heating (solid curves) and 2 nd heating (dashed curves).

Figure 8 :

 8 Figure 8: Typical stress/strain curves of films based on various reactive diluents at same hard segment content.

Table 1 :

 1 Conversion and appearance of NIPUA coatings.

	Coating code 1 Reactive diluent	CC=C 2 (meq/g)	DE 3 (%)	χ 4 (%)	Aspect 5	Thickness (thin/thick) (µm)
	NIPUA-H0	-	0.8	52	75	Y, S, T	28 ± 4 160 ± 11
	NIPUA-H10	HDDA	2.5	56	87	Y, S, T	26 ± 4 176 ± 10
	NIPUA-B20	BHECA	2.5	54	84	Y, S, T	22 ± 6 161 ± 3
	NIPUA-U20	UDMA	2.3	59	76	Y, S, T	30 ± 5 137 ± 10
	NIPUA-H20	HDDA	4.0	63	> 95	Y, S, T	32 ± 8 178 ± 4
	NIPUA-H30	HDDA	5.2	65	> 95	Y, SR, F, T	41 ± 7 168 ± 8
	NIPUA-H40	HDDA	6.3	67	> 95	Y, SR, T	33 ± 4 178 ± 4
	NIPUA-H50	HDDA	7.2	71	> 95	Y, SR, T	27 ± 8 205 ± 6

Table 2 :

 2 Extractables and swelling percentages of NIPUA coatings.

	Coating code	Reactive diluent	Mc(A-A) 1	Thin Films τEx (%) Q (%)	Thick Films τEx (%) Q (%)	Obs. 2
	NIPUA-H0	HDDA	5650	2.4 ± 0.4 180 ± 27 5.3 ± 1.1 313 ± 14	ND
	NIPUA-H10	HDDA	1780	4.3 ± 0.3	128 ± 6	3.8 ± 0.7 159 ± 16	ND
	NIPUA-H20	HDDA	1130	6.0 ± 1.0	59 ± 12	6.6 ± 0.3	144 ± 5	ND
	NIPUA-H30	HDDA	870	2.8 ± 0.2	46 ± 2	11.4 ± 1.9	90 ± 5	D
	NIPUA-H40	HDDA	720	1.7 ± 0.3	17 ± 1	6.4 ± 1.3	70 ± 1	ND
	NIPUA-H50	HDDA	630	1.4 ± 1.0	17 ± 2	2.3 ± 0.3	61 ± 7	ND
	NIPUA-B20	BHECA	2000	1.5 ± 0.7	93 ± 2	2.2 ± 0.5 221 ± 15	ND
	NIPUA-U20	UDMA	1780	5.0 ± 0.3	120 ± 5	5.7 ± 0.3	175 ± 8	ND
	1 Average molecular weight between two acrylate functions.
	2 ND = No or little degradation, D = Degradation, D+ = Significant degradation.

ACKNOWLEDGEMENTS

Authors thank Mäder Research company for the financial support. This manuscript is a tribute to the 50-year anniversary of the French Polymer Group (Groupe Français des Polymères -GFP).

For coatings based on the non-urethane HDDA diluent (NIPUA-H10 to NIPUA-H50) as well as those without any reactive diluent (NIPUA-H0), the degradations of the hard and soft segments were overlapped (Figure 4 and5) suggesting that the crosslinking reaction increases Tmax of the HS part. [START_REF] Yilgör | Critical parameters in designing segmented polyurethanes and their effect on morphology and properties: A comprehensive review[END_REF] However, T5% decreased from 318 to 260°C with the increase of HDDA content within the coating up to 40 wt.%, and increased again to 314°C for 50 wt.% of HDDA. This evolution could be ascribed to the presence of volatile compound such as residual solvent within these materials and is in quite consistency with the values of extractable percentages ( 8 , Table 3, thick films). Coatings based on reactive diluents bearing urethane groups (BHECA and UDMA) exhibited intermediate T5% (294 and 291°C, respectively) and Tmax values for the urethane degradation step (Figure 4).

The thermal properties of the NIPUA coatings were measured by DSC. Typical DSC curves are presented in Figure 6. The thermal parameters are displayed in Table 3. Tm value of PTMO soft segments decreased from 23°C (within A-C6-2000 prepolymer) to 13°C after photocrosslinking (NIPUA-H0). This value fell to around 10°C when HDDA is used at 10 to 30 wt.% and was not observed at 40 and 50 wt.%. ΔH ; values also decreased from 47 to 0 J/g with the increase of HDDA content from 0 to 50 %, i.e. decrease of MA-A from 5650 to 630 g/mol. This result suggests that the crystallinity of the soft segments was reduced by increasing the cross-linking density, which is consistent with the literature data. [START_REF] Li | Synthesis and properties of non-isocyanate aliphatic crystallizable thermoplastic poly(ether urethane) elastomers[END_REF] Tc values decreased from -3 to -21°C after crosslinking of A-C6-2000 in the absence of reactive diluents (NIPUA-H0). In the presence of reactive diluents at 10 to 30 wt.%, cold crystallization was observed at around -40°C, which disappeared for a composition of 40 and 50 wt.%. ΔH 6 values decreased with crosslinking and the content of reactive diluent. NIPUA-U20 and NIPUA-B20 coatings exhibited Tm values of 7 and 9°C with ΔH ; values of 18 and 29 J/g, respectively. Tc values were of -34 and -43°c with ΔH 6 values of 13 and 21 J/g, respectively. They have very close properties In the case of NIPUA-H0, the high elasticity properties come from the length of the A-Ol oligomer ( 6 = 5650 g/mol). Above 400% elongation, the high stress at break could result from a crystallization phenomenon induced by the axial deformation, bringing the polymer chains physically closer together and ordering them in relation to each other and thus promoting their interactions. [START_REF] Oprea | The synthesis and properties of binary acrylate oligomer mixtures and their blends with different soybean oil contents[END_REF] With the introduction of HDDA, the higher cross-linking density generate additional acrylate/soft segment interactions, which could hinder crystallization. This could explain the significant drop in mechanical strength (σr) from approximately 12 to 5 MPa. When the wt.% of HDDA is increased from 10 to 50%, σr increases with the cross-linking density as expected. [START_REF] Maurya | A Review on Acrylate-Terminated Urethane Oligomers and Polymers: Synthesis and Applications[END_REF] Properties provided by each type of reactive diluent were compared at the same molar fraction (CC=C = 2.3 -2.5 meq/g, Table 4). The use of urethane reactive diluent (at 20 wt.%) slightly increases the

Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time due to technical and time limitations.


Agathe Berly

Cécile Manaouil

Alain Dervaux

L'intelligence artificielle peut-elle aider à estimer le risque de récidive dans les comportements violents ?

Keywords:

Médecine et Droit

Exercice professionnel L'intelligence Artificielle peut-elle aider à estimer le risque de récidive dans les comportements violents ? Can Artificial Intelligence help estimate the risk of recidivism in violent behavior? Agathe Berly, psychiatre au CH de Saint Quentin 1 avenue Michel de l'Hospital BP 608 ,0232121 Saint Quentin agathe.berly@hotmail.fr Cécile Manaouil, professeur de médecine légale au CHU d'Amiens, Alain Dervau, professeur en psychiatrie au CHU d'Amiens

Résumé

En psychiatrie légale, les magistrats posent la question de l'existence d'un risque de récidive et de la dangerosité aux experts psychiatres. Les études de suivi en psychiatrie légale ont montré que les éléments psychiatriques prédictifs de récidive étaient liés essentiellement aux pathologies mentales graves, consommations de toxiques, addictions, niveaux élevés d'impulsivité, insight faible, troubles de personnalité associés, en particulier troubles de personnalité antisociale. Il existe aussi des facteurs de protection, en particulier l'observance des traitements. Compte tenu de la complexité des facteurs de risque et de protection psychiatriques et criminologiques, l'intelligence artificielle (IA) peut-elle aider psychiatres et magistrats à améliorer la prédictivité des récidives ? Méthodes : revue systématique de la littérature sur les applications de l'IA dans la prédiction des récidives en Psychiatrie légale, réalisée selon les critères PRISMA, utilisant les mots-clés « Artificial Intelligence », « Recidivism », « PersonalityDisorder », « Impulsive Behavior », « Alcohol abuse », « Drug Abuse », « Schizophrenia », « Bipolardisorder » sur les bases de données PubMed, Science Direct, Clinical Trial et Google Scholar. Résultats : La grande majorité des études est issue de revues juridiques ou informatiques et très peu des bases de données médicales. Les études évaluant l'IA en Psychiatrie légale ont utilisé le plus souvent le Machine Learning à partir de données sociodémographiques, sociologiques, criminologiques, notamment l'âge de la première infraction et le nombre de condamnations antérieures. A ce jour, il n'y a que très peu d'études évaluant des paramètres psychiatriques, portant surtout sur les troubles de personnalité psychopathiques. Discussion /conclusion : Les applications de l'IA en Psychiatrie légale sont encore très prématurées. Cependant, certains critères psychiatriques devraient avoir une place plus importante dans ce champ, en particulier ceux issus des échelles HCR-20 de Webster et PCLR de Hare. L'enjeu sera également de trouver les mots-clés comportementaux, psychologiques et psychiatriques pertinents à inclure en IA.

Mots clés: Récidive( intelligence artificielle)

En 2017, le taux de récidive était estimé à 41% pour les délits et 7,2% pour les crimes [START_REF]Les chiffres-clés de la justice[END_REF]. En raison de facteurs économiques, politiques et sécuritaires, l'estimation du risque de récidive est capitale. L'amélioration de l'exactitude prédictive du risque de récidive permettrait d'améliorer l'efficacité du processus décisionnel en matière de justice pénale, la sécurité de la communauté et la réadaptation des délinquants en adaptant les mesures alternatives à l'incarcération. Plusieurs paradigmes se sont chevauchés en commençant par le jugement clinique reposant sur une intuition guidée par l'expérience, qui s'est souvent avéré peu précis car trop sensible à l'influence des traditions et de la politique par exemple [START_REF] Hanson | The accuracy of recidivism risk assessments for sexual offenders : A meta-analysis of 118 prediction studies[END_REF]. L'essor de l'evidence based médecine, fondée sur des preuves, a permis l'apparition des méthodes actuarielles reposant sur des données reliant certains facteurs au risque de récidive. Plusieurs versions se sont succédées, permettant de prendre en compte des facteurs dynamiques. La plus utilisée reste l'Historical Clinical Risk-20 (HCR-20) qui inclut l'échelle de psychopathie de Hare (PCL-R) (3) L'HCR-20 (figure 1) est fréquemment utilisé et validé dans les pays limitrophes comme la Belgique. Elle présente plusieurs catégories d'items, à savoir des facteurs chronologiques, cliniques et de gestion du risque. Les facteurs de risque identifiés par cette échelle sont connus pour être susceptibles de participer à l'émergence d'un acte violent. L'évaluation de l'item « Psychopathie » s'appuie sur les résultats obtenus lors de la passation de l'échelle de psychopathie de Hare ou PCL-R (figure 2). Ces méthodes ont toujours un franc succès mais, devant la disponibilité croissante de très grands ensembles de données, les outils issus de l'IA semblent prometteurs, notamment les arbres de décision, forêts aléatoires et réseaux de neurones artificiels.

I Résultats

Plusieurs études, majoritairement réalisées aux USA, ont constaté un meilleur potentiel prédictif concernant les outils de l'IA, parfois même statistiquement significatif. Ces travaux ont mis en évidence que la place des prédicteurs était essentielle comme l'âge, le sexe, les condamnations antérieures et l'âge lors de la première infraction (4). Peu de prédicteurs psychiatriques entrent en compte dans ces outils, le potentiel prédictif des caractéristiques sociodémographiques et criminologiques étant supérieur. Le lien entre les troubles psychiatriques et le risque de violence est significatif. Les facteurs psychiatriques récurrents ayant un lien avec la violence et la récidive sont la présence d'un trouble mental grave, notamment la schizophrénie ou le trouble bipolaire (5), la consommation de toxiques, notamment l'alcool, les troubles de la personnalité associés, notamment le trouble de personnalité antisociale [START_REF] Fazel | Risk factors for interpersonal violence : an umbrella review of meta-analyses[END_REF], des hauts degrés d'impulsivité, retrouvés dans la personnalité antisociale, le manque d'insight, les troubles neurocognitifs, type troubles exécutifs et troubles de la mémoire. D'autres facteurs sont en lien avec une diminution du risque de violence comme un bon insight chez les patients atteints de pathologies mentales, la bonne observance du traitement, notamment les molécules comme la clozapine [START_REF] Patchan | Clozapine in Reducing Aggression and Violence in Forensic Populations[END_REF] et les traitements antipsychotiques d'action prolongée [START_REF] Mohr | Long-acting injectable antipsychotics for prevention and management of violent behaviour in psychotic patients[END_REF], les thérapies associées, notamment la remédiation cognitive ou les thérapies cognitivo-comportementales. Concernant les prédicteurs psychiatriques, au niveau international les deux outils les plus utilisés en termes d'évaluation de la violence et de la récidive sont l'HCR-20 et la PCL-R qui est décrite comme un facteur prédictif clé de la récidive [START_REF] Dolan | Violence risk prediction. Clinical and actuarial measures and the role of the Psychopathy Checklist[END_REF]. Elle permet d'évaluer le trouble de la personnalité antisociale, qui est significativement associée à un risque de violence.

II Limites

Concernant l'effet « black-box », qui fait référence à l'idée que des données sont entrées dans l'algorithme et qu'une prévision est générée sans explication claire de la façon dont l'algorithme a pris la décision, certains outils pourraient être préférés à d'autres dans l'estimation du risque de récidive en raison de leur plus grande transparence, et ce au détriment d'une baisse de la puissance prédictive. Des travaux cherchent à améliorer l'interprétabilité de l'IA. Concernant l'utilisation de la « race » comme prédicteur, les avis divergent, certains estimant que l'ethnie est un facteur important pour prédire la récidive, d'autres non. Même si l'ethnie n'est pas incluse comme prédicteur, d'autres pourraient ajouter indirectement une composante ethnique (certains quartiers sont fortement corrélés à l'ethnie en raison de la densité de minorités ethniques). Sur le sujet très sensible, en France, sur ce qui concerne les origines raciales ou ethniques, la loi du 6 janvier 1978, dite « loi informatique et libertés » interdit de recueillir et d'enregistrer des informations faisant apparaître, directement ou indirectement, les origines ainsi que les appartenances religieuses des personnes. L'Article 226-19 du Code pénal dispose que « Le fait, hors les cas prévus par la loi, de mettre ou de conserver en mémoire informatisée, sans le consentement exprès de l'intéressé, des données à caractère personnel qui, directement ou indirectement, font apparaître les origines raciales ou ethniques, les opinions politiques, philosophiques ou religieuses, ou les appartenances syndicales des personnes, ou qui sont relatives à la santé ou à l'orientation sexuelle ou à l'identité de genre de celles-ci, est puni de 5 ans d'emprisonnement et de 300 000 euros d'amende ». Ainsi on peut faire des statistiques sur la nationalité des personnes (figure 3) mais pas sur leur ethnie sauf dispositions particulières prévues par la loi. Les chiffres clés de l'administration pénitentiaire publiés chaque année sur le site www.justice.gouv.fr fournissent la nationalité des personnes écrouées mais pas leur ethnie. Il est à priori toutefois possible de faire des statistiques incluant l'origine ethnique : la loi donne dérogation aux chercheurs pour étudier les origines ethniques et religieuses, selon certains critères très encadrés. C'est la Commission nationale de l'informatique et des libertés (CNIL) qui étudie chaque enquête, en fonction de la finalité des recherches, de l'institut qui les mène, du consentement des personnes concernées et du respect de leur anonymat. Néanmoins, il est douteux qu'une dérogation soit accordée pour recenser l'origine ethnique de personnes incarcérées. Aux USA, les chercheurs plus « pragmatiques » utilisent toutes les données pouvant participer à l'amélioration de la prédiction.

L'interprétabilité et le choix des prédicteurs pourraient donc déterminer l'acceptabilité de ces nouvelles méthodes de prévision. D'un point de vue éthique, l'évaluation de la dangerosité et du risque de récidive répond à une demande politique, la préservation de l'ordre social, mise en oeuvre par des magistrats éclairés par l'expérience clinique de l'expert psychiatre. La mission de l'expert porte de moins en moins sur le diagnostic et de plus en plus sur le pronostic : médecins et magistrats n'ont pas le même but. Les données utilisées, qu'elles soient judiciaires ou médicales, sont très sensibles. La question se pose de savoir où seront stockées les données et qui y aura accès ? Ces données nécessiteront un cadre juridique strict pour les utiliser. Concernant les moyens de recours, il est important de se demander quelle responsabilité pourra être recherchée en cas d'erreur de prédiction Concernant les psychiatres en France, deux courants s'opposent quant à l'utilisation d'outils d'aide à la prédiction [START_REF] Abondo | Évaluation du risque de récidive : de la nécessité d'une evidence-based expertise[END_REF]. Beaucoup s'opposent à ces nouveaux outils de crainte de voir l'individu évalué réduit à un score chiffré. Certains courants en psychiatrie peuvent également être à l'origine d'un clivage, responsable d'un rejet des nouvelles approches alternatives. Cependant, l'expert ne peut pas ignorer la validation de nouvelles connaissances intéressant son champ de compétences et rester enfermé dans ses certitudes et son courant idéologique. Il convient à l'expert de se positionner vis-à-vis de ces nouveaux outils, de les appréhender comme un moyen d'investigation complémentaire du jugement clinique, en prenant en compte leurs performances et leurs limites.

III Perspectives

Associé à une bonne documentation des liens entre psychiatrie et violence, il serait intéressant d'ajouter ces éléments à l'IA même si plusieurs travaux ont évoqué la meilleure prédictivité des critères de dangerosité criminologique. La question des mots clés à utiliser se pose. En effet, si les données sont extraites de documents judiciaires, les éléments cliniques ne seront pas inscrits en termes de clinique sémiologique mais en terme profane (ex : impulsivité = agit sans réfléchir, épisode maniaque = s'est promené nu sur l'autoroute, traitement = Risperdal R, « piqûre tous les mois »). Ceci pose une limite à l'inclusion d'éléments psychiatriques au sein de l'IA, à laquelle il faudrait réfléchir. De plus, comment l'ordinateur peut appréhender « ce qui n'est pas » quand l'expert fait état des éléments cliniques recherchés lors de son expertise, mais absents. Une alternative serait d'inclure les critères des outils HCR-20 et PCL-R qui représentent des éléments prédictifs forts. Il est également très important, dans l'utilisation de ces nouveaux outils, de ne pas négliger les facteurs de protection qui pourraient faire chuter le risque de récidive.

Les recherches effectuées dans le domaine de l'IA n'ont pas pour but de mettre en évidence un outil capable de se substituer à l'évaluation de l'expert ou à la décision du juge, il s'agirait d'une aide à prendre la décision la plus éclairée, juste, objective et équitable possible, la prédiction parfaite à 100% restant impossible. Malgré les progrès considérables accomplis par

Figure 1 :Figure 2 :Figure 3 :

 123 Figure 1 : Historical Clinical Risk-20 (HCR-20)