Photosensitive polymers with cinnamate units in the side position of ...

Photosensitive polymers with cinnamate units in the 

side position of chains: Synthesis, monomer reactivity 

ratios and photoreactivity 

Rachid Mahy a , Boufelja Bouammali a, *, Abdelkader Oulmidi a , Allal Challioui a , 

Daniel Derouet b , Jean Claude Brosse b 

a Laboratoire de Photochimie et Chimie Macromoléculaire, Département de Chimie, Faculté des Sciences, Université Mohamed I, 

60000 Oujda, Morocco 

b LCOM-Chimie des Polymères (UMR du CNRS UCO2M N °6011), Université du Maine, Faculté des Sciences, 

Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France 

Abstract 

Received 6 April 2006; received in revised form 24 May 2006; accepted 26 May 2006 

Available online 17 July 2006 

Ethyl a-cyano-4-(methacryloxy)cinnamate was synthesized to prepare new photosensitive polymers. Homopolymerization 

and copolymerizations were carried out in solution in chloroform at 65 °C using AIBN as an initiator. Methyl methacrylate 

was chosen as comonomer for the studies of copolymerzation. The structures formed were characterized by IR 

and 1 H NMR spectroscopies. The values of reactivity ratios of the comonomers calculated according to the Finneman– 

Ross method indicated that the reactivity of the synthesized photosensitive monomer is lower than that of MMA. Thin 

films of the obtained polymers were prepared to study their ability to crosslink under UV irradiation. The photodimerization 

of the cinnamate moieties was characterized. 

Ó 2006 Elsevier Ltd. All rights reserved. 

Keywords: Photocrosslinkable polymers; Photodimerization; Cinnamate derivatives; Knoevenagel reaction 

1. Introduction 

European Polymer Journal 42 (2006) 2389–2397 

In recent years, there has been widespread 

research into the synthesis and the applications of 

photosensitive polymers. These polymers are extensively 

used as photoresists for the manufacture of 

* 

Corresponding author. Tel.: +212 0 36 50 06 01/02; fax: +212 

036500603. 

E-mail addresses: a_Bouammali@Yahoo.fr (B. Bouammali), 

Daniel.Derouet@univ-lemans.fr (D. Derouet). 

0014-3057/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. 

doi:10.1016/j.eurpolymj.2006.05.031 

EUROPEAN 

POLYMER 

JOURNAL 

www.elsevier.com/locate/europolj 

numerous industrial products, for instance, integrated 

circuits, printing materials, coatings, paint, 

compact discs, cathode ray tubes, etc. [1–4]. Polymers 

containing cinnamate groups either in the 

backbone or in the side position of the chains 

undergo crosslinking upon irradiation. The best 

known is the polyvinyl cinnamic acid ester [5]. The 

capability of these polymers to crosslink is due to 

the carbon–carbon double bonds of the a,b-unsaturated 

carbonyl groups which undergo [2p +2p] 

cycloaddition reactions under irradiation. These

2390 R. Mahy et al. / European Polymer Journal 42 (2006) 2389–2397 

O 

HO C 

H 

H 3C 

H 2C 

CN 

CO 2Et 

photosensitive polymers are regarded as negativetype 

photoresists [6,7]. 

The substitution of the double bond of cinnamate 

group can affect its photosensitivity. It was 

reported that the withdrawing groups such as cyano 

group at the a-position of carbonyl function 

enhances the photoreactivity of cinnamate unit [8]. 

Brosse et al. [9] and Remmas et al. [10,11] have 

prepared and tested for photosensitivity different 

polystyrenic polymers with pendant cinnamate 

groups substituted on a-position by carboxylate 

and cyano groups. 

This article deals with the synthesis of new monomer 

[Ethyl a-cyano-4-(methacryloxy)cinnamate], 

its polymerization and copolymerization with 

C 

O 

CH 2 

+ 

O 

piperidine 

(pyridine) 

CN 

CH C 

CO2Et methyl methacrylate (Schemes 1 and 2). Monomer 

reactivity ratios and the ability to crosslink of the 

obtained polymers under UV irradiation were also 

investigated. 

2. Experimental 

2.1. Materials 

CN 

HO CH C 

CO2Et 1 2 3 (80 %) 

4 (75 %) 

1) Et 3 N / CH 2 Cl 2 

2) H 2 C=C(CH 3 )-COCl 

Scheme 1. Synthesis of ethyl a-cyano-4-hydroxycinnamate 3 and ethyl a-cyano-4-(methacryloxy)cinnamate 4. 

H 2C 

C 

EtO 2 C 

CH 3 

4 

C 

O 

CH 

C 

O 

CN 

+ 

MMA 

AIBN/ CHCl 3 

65ºC 

CH 2 

EtO 2 C 

C 

C 

O 

HC 

CH 3 

C 

CN 

p 

CH 2 

5 :Homopolymer (q=0) 

6 : Copolymer 

Scheme 2. Synthesis of photosensitive homo- and co-polymers coming from 4. 

O 

C 

q 

CO2CH3 Solvents were distilled before use according to 

the procedures described in Perrin book [12] p- 

Hydrobenzaldehyde and AIBN were recrystallized 

in methanol. Methyl methacrylate was purified as 

follows: after washing twice with an aqueous solution 

of NaHCO3 (5%), and then twice with water, 

CH 3

it was dried over Na2SO4, and finally the dried filtrate 

was distillated under reduced pressure. Methacryloyl 

chloride was purified by distillation under 

vacuum. Ethyl cyanoacetate was used as received. 

2.2. Apparatus 

Melting points were determined on a Bütchi 

apparatus. UV spectra were carried out on a Varian 

spectrophotometer (Cary Win UV B1O 100/300). 

Infrared spectra were recorded on a Perkin–Elmer 

1750 Fourier-transform spectrometer. 1 H and 13 C 

NMR spectra were recorded on Avance DPX200 

or Bruker AC 400 operating at 400.13 MHz for 

1 H and 100 MHz for 13 CinCDCl3 or DMSO-d 6 

with tetramethylsilane (TMS) as internal reference. 

The weight- and number-average molecular weights 

were determined by Size Exlusion Chromatography 

(SEC) on a Spectra SYSTEM AS1000 autosampler 

system, equipped with a guard column (Polymer 

Laboratories, PL gel 5 lm Guard, 50 · 7.5 mm) 

and two columns (Polmer Laboratories, 2 PL gel 

5 lm MIXED-D columns, 300 · 7.5 mm) connected 

in series, and a Spectra SYSTEM RI-150 detector. 

Analyses were performed at 35 °C. THF was used 

as mobile phase at a flow rate of 1 ml min 1 . The 

system was calibrated using low polydispersity polystyrene 

standards (483–580 · 10 3 g mol 1 ). The 

photocrosslinking studies were peformed using a 

B100A Ultraviolet lamp emitting from 300 to 

400 nm (100 w; k max = 365 nm). 

2.3. Synthesis of ethyl a-cyano-4-hydroxycinnamate 3 

A pyridine solution (7.5 ml) of p-hydoxybenzaldehyde 

1 (25 mmol), ethyl cyanoacetate 2 (25 mmol) 

and piperidine (2 drops) was refluxed for 1 h in a 

round bottom flask fitted with a condenser. Then, 

the solution was poured drop by drop into a flask 

containing 100 ml of water and 25 g of crushed ice. 

The mixture was stirred until a product in suspension 

was formed. The precipitated material was filtered, 

washed with water, and then recrystallized in 

ethanol. Yield: 80%; mp 173 °C; IR (KBr): 3299 

(OH), 2228 (C„N), 1714 (C@O), 1612 (C@sC); 1 H 

NMR (400 MHz, DMSO-d 6): d (ppm) 8.17 (s, 1H, 

HC@C), 7.95 (d, J = 11.4 Hz, 2H, Ar–H 2,6), 6.90 

(d, J = 11.4 Hz, 2H, Ar–H 3,5), 4.25 (q, J = 7.2 

HZ, 2H, CH3–CH2–O), 1.27 (t, J = 7.2 Hz, 3H, 

CH3–CH2–O); 13 C NMR (100 MHz, DMSO-d6): d 

(ppm) 164.1 (CO2Et), 162.6 (C4), 154.4 (CH@C), 

133.8 (C2 and C6), 122.0 (C1), 116.6 (C3 and C5), 

R. Mahy et al. / European Polymer Journal 42 (2006) 2389–2397 2391 

116.6 (CN), 98.4 (CH=C), 63.0 (CH3–CH2–O), 

13.9 (CH3-CH2–O). 

2.4. Synthesis of a-cyano-4-(methacryloxy)cinnamate 

4 

A solution of 3 (0.012 mol) in dichloromethane 

(12 ml) was introduced in a three necked roundbottom 

flask and cooled at 0 °C using an ice bath. 

Solutions of methacryloyl chloride (0.018 mol) 

in dichloromethane (6 ml) and triethylamine 

(0.018 mol) in dichloromethane (6 ml) were added 

simultaneously and dropwise from tow dropping 

funnels into the stirred mixture. At the end of addition, 

the ice bath was removed and the stirring was 

maintained for 12 h at room temperature. The 

formed triethylammonium chloride was filtered off 

and the filtrate was washed twice with a solution 

of sodium bicarbonate, twice with water, and then 

dried over sodium sulfate. Finally, the solvent of 

the dried filtrate was evaporated under reduce pressure 

and the crude product was recrystallized in ethanol. 

Yield: 75%; mp: 109 °C; IR (KBr): 2223 

(C„N), 1743 and 1716 (C@O), 1614 (C@C); 1 H 

NMR (400 MHz, DMSO-d6): d (ppm) 8.25 (s, 1H, 

HC@C), 8.05 (d, J = 11.4 Hz, 2H, Ar–H2,6), 7.30 

(d, J = 11.4 Hz, 2H, Ar–H3,5), 6.40 and 5.8 (s, 2H, 

H2C@C methacrylate), 4.38 (q, J = 7.2 Hz, 2H, 

CH3–CH2–O), 2.09 (s, 3H, CH3–CO), 1.42 (t, 

J = 7.2 Hz, 3H, CH 3–CH 2–O); 

13 C NMR 

(100 MHz, DMSO-d 6): d (ppm) 164.3 (CO 2Et), 

161.6 (CO-methacrylate), 153.8 (C4), 152.9 

(CH@C), 134.6 (H2C@C-methacrylate), 131.8 (C2 

and C6), 128.1 (C1), 127.4 (H2C@C methacrylate), 

121.8 (C3 and C5), 114.6 (CN), 101.9 (CH@C), 

62.0 (CH3–CH2–O), 17.5 (CH3-methacrylate), 13.3 

(CH 3–CH 2–O). 

2.5. Synthesis of homopolymer 5 

In a round-bottom flask fitted with a condenser 

were introduced 0.23 mmol of monomer 4, 5 ml of 

chloroform, and 0.023 mmol of AIBN (1% compared 

to 4). The mixture was swept by nitrogen, 

and then heated at 65 °C. After the required time 

(8 h), the obtained mixture was poured in a large 

excess of methanol (20 ml). The precipitated polymer 

was washed with methanol, then purified by 

repeated reprecipitation into methanol from solution 

in chloroform, and finally dried under vacuum. 

Yield: 92%; IR (KBr): 2225 (C„N), 1756 and 1716 

1 

(C@O), 1613 (C@C); H NMR (400 MHz,


DMSO-d6): d (ppm) 8.2 (1H, HC@C), 8.0 (2H, Ar– 

H2,6), 7.1 (2H, Ar–H3,5), 4.4 (2H, CH3–CH2–O), 

0.5–2.2 (backbone protons and CH3–CH2–O–). 

2.6. Synthesis of copolymers 6 

Five copolymerization experiments were performed 

using 4 and MMA as comonomer. Various 

monomer molar ratios (20/80, 30/70, 50/50, 70/30 

and 80/20) were considered. Appropriate amounts 

of monomers (total concentration = 0.47 mol l 1 ), 

initiator (AIBN, 1% compared to 4), and chloroform 

(5 ml) were introduced in a round-bottom 

flask fitted with a condenser. The mixture was 

placed under nitrogen atmosphere, and then stirred 

at 65 °C for 8 h. The formed copolymer was purified 

according to the same procedure as for the homopolymer. 

Poly(4-co-MMA) 6: Yield: 60–95%; IR 

(KBr): 2224 (C„N), 1750 and 1716 (C@O), 1613 

(C@C); 1 H NMR (400 MHz, CDCl3): d (ppm) 8.3 

(1H, HC@C–), 8.1 (2H, Ar–H 2, 6), 7.3 (2H, Ar– 

H 3,5), 4.4 (2H, CH 3–CH 2–O–), 3.6 (3H, –CO 2CH 3), 

0.8–2.3 (backbone protons and CH 3–CH 2–O–). 

2.7. Photoreactivity measurements 

The photochemical reactivity of the synthesized 

homo- and co-polymers was measured as follows: 

The copolymer solution in THF was cast on a 

quartz plate and dried under vacuum at 40 °C for 

1 h. After drying, the film formed on the plate was 

irradiated using the B100A Ultraviolet lamp placed 

at a distance of 5 cm for different time intervals. 

After each exposure interval, UV and IR spectra 

of the sample were recorded, and the photocrosslinking 

rate was determined by following the intensity 

decrease of the cinnamate absorption band 

(310 nm and 1613 cm 1 , respectively, for UV and 

IR). 

3. Results and discussion 

3.1. Preparation of ethyl a-cyano-4hydroxycinnamate 

3 and a-cyano-4- 

(methacryloxy)cinnamate 4 

Compound 3 was prepared by Knoevenagel condensation 

of p-hydroybenzaldehyde 1 with ethyl 

cyanoacetate 2 in presence of piperidine as a basic 

catalyst. Then 3 was esterified by methacryloyl chloride 

in presence of triethylamine to give the methacrylate 

monomer 4 (Scheme 1). 

3 and 4 were obtained in good yields (80% and 

75%, respectively) and the analytical data (see Section 

2) fully supported the structure of 3 and 4. 

3.2. Homopolymerization of 4 

Radical homopolymerization of 4 was initiated 

with azoisobutyronitrile (AIBN). It was performed 

at 65 °C in chloroform (Scheme 2). After 8 h of 

reaction, polymer 5 was obtained in 92% yield. It 

showed good solubility in butanone, THF, CH2Cl2, 

CHCl3, benzene, toluene, DMF and dioxane. 

The weight- and number-average molecular 

weights of 9600 and 6200, respectively, were determined 

by SEC. The value of polydispersity index 

(I = 1.7) which is close to 2, suggests a tendency 

for chain termination by dispropotionation. 

Homopolymer 5 was characterized by IR and 1 H 

NMR. In IR, strong absorption bands characteristic 

of the carbonyles of methacrylate and cinnamate 

functions were noted at 1756 cm 1 and 

1716 cm 1 , respectively. A weak absorption band 

at 1613 cm 1 was attributed to CH@C unsaturations. 

An absorption band at 1595 cm 1 was 

assigned to aromatic C@C stretching vibration. 

The 1 H NMR spectrum of 5 shows resonances at 

d = 8.0 and 7.1 ppm due to aromatic protons. The 

proton of the CH=C unsaturations is noted at 

d = 8.2 ppm. Signal at d = 4.4 ppm corresponds to 

CH2 protons of ethoxy groups. The CH3 protons 

of ethoxy groups and the backbone protons rise at 

0.5–2.2 ppm (Fig. 1). 

A progress of 4 polymerization performed in 

deuterated chloroform was followed by 1 H NMR 

(Fig. 2). The incorporation of monomer 4 in polymer 

was determined form 1 H NMR spectra by comparing 

the relative intensities of the methacrylic 

methylene protons of the residual monomer 

(d = 6.40 and 5.80 ppm) to protons at d = 7.8 and 

8.5 ppm (CH@C and Ar–H2,6) of both residual 

monomer and monomer incorporated in polymer. 

According to the general equation of the polymerization 

rate [13] (Eq. (1)), the kp= ffiffiffiffi p 

kt ratios were 

calculated (kd = 2.53 10 5 s 1 determined at 65 °C 

and f = 0.5 [14]). 

ffiffiffiffi 

kt 

p 

Ln½M 0Š=½M tŠ ¼ðkp= 

pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 

Þ 2 2f ½I 0Š=kd: 

½1 expð kd t=2ÞŠ ð1Þ 

where [M0] and [Mt] are the monomer concentrations 

at times 0 and t, respectively, and [I0] is the initiator 

concentration. kd, kp and kt are the reaction

Conversion of 4 (%) 

80 

70 

60 

50 

40 

30 

20 

10 

0 

9 

a 

e 

CH2 d 

CH3 C 

n 

c b 

a 

O 

C O 

f 

CH2 

g 

CH3 

O 

CO 

c' b' 

CH C 

CN 

b,b’ 

8 

rate constants of initiator decomposition, propagation 

and termination, respectively. f is the initiator 

efficiency. 

The plot of Ln[M0]/[Mt] versus [1 exp( kd Æ t/2)] 

gives slope of 1.2 witch lead to the kp= ffiffiffiffi p 

kt ratio 

of 0.04 mol 1/2 l 1/2 s 1/2 

([I0] = 4.7·10 3 mol l 1 ) 

(Fig. 3). Compared to MMA (kp= ffiffiffiffi p 

kt ¼ 0:12; T = 

60 °C) [13], monomer 4 is about three times less reactive. 

This difference can be explained by the steric 

hindrance and resonance radical stabilization of 

cinamate group. 

c,c’ 

0 1 2 3 4 5 6 7 8 9 10 

Times (h) 

Fig. 2. Progress of radical polymerisation of 4 versus time. 


7 

6 

5 

f 

4 

Fig. 1. 1 H NMR spectrum of homopolymer 5. 

Ln (Mo/Mt) 

3 

0.4 

0.35 

0.3 

0.25 

0.2 

0.15 

0.1 

0.05 

0 

2 

1 

d,e,g 

-1 

3.3. Copolymerization of 4 with methylmethacylate 

The free radical copolymerization of 4 with 

MMA was conducted in chloroform for 8 h at 

65 °C using AIBN as an initiator (Scheme 2). Various 

monomer ratios were considered (Table 1). The 

copolymers 6 were obtained with good yields (60– 

95%). They were easily soluble in most of the 

organic solvents such as butanone, THF, CH2Cl2, 

CHCl3, benzene, toluene, DMF and dioxane. 

The values of mass average molecular weight 

(M wÞ and number average molecular weight (M nÞ 

0 

y= 1.1975x- 0.0214 

0 0.1 0.2 0.3 0.4 

1-exp(-2.53*10-5t) 

Fig. 3. Variation of Ln[M0]/[Mt] versus [1 exp( kd Æ t/2)] for 

polymerizations of 4 (slope = 1.2, [I 0] = 4.7 10 3 · mol l 1 , 

k d = 0.85 · 10 5 s 1 , and f = 0.5).


Table 1 

Yield and molecular weight data for the copolymerizations of 4 

with MMA 

Copolymer f Yield (%) M w M n I 

6a 0.2 60 10300 5400 1.9 

6b 0.3 85 13700 7700 1.8 

6c 0.5 75 17900 7500 2.4 

6d 0.7 80 ND ND ND 

6e 0.8 95 ND ND ND 

f: Molar fractions of 4 in feed; I: Polydispersity index; ND: not 

determined. 

and polydispersity index (I) of copolymers 6 are 

determined by size exclusion chromatography and 

listed in Table 1. The data indicate that M w 

and M n were found to range from 10300 to 

17900 g/mol and 5400 to 7700 g/mol, respectively. 

As for the homopolymerization, polydispersity 

indexes values of copolymers 6 (1.8–2.4) suggest a 

strong tendency for chain termination by disproportionation. 

The chemical structures of copolymers 6 were 

confirmed by spectroscopic methods (IR and 1 H 

NMR). 

t=0h 

t=4h 

t=6h 

0 h 

4 h 

6 h 

8 h 

t=8h 

9.0 

a 

b,b' 

8.0 

g 

H 2C=C of4 

c,c' 

f 

CH 2 

CH 3 

7.0 

O 

CN 

CO 

6.0 

a 

CH 

c 

c' 

H 2C=C of MMA 

5.0 

b 

b' 

IR spectra of the copolymers showed strong 

absorption bands characteristic of the carbonyles 

of methacrylate and cinnamate functions at about 

1750 cm 1 and 1716 cm 1 , respectively. A weak 

absorption band at 1613 cm 1 was assignable to 

CH@C unsaturations of cinnamate groups. 

In case of 1 H NMR, Fig. 4 (case where f = 0.3 

and t = 8 h) shows the representative spectra of 

copolymer 6. It exhibits broad signals at d = 7.3 

and 8.1 ppm due to aromatic protons. The proton 

of the CH@C unsaturations is observed at 

d = 8.3 ppm. Peaks at d = 4.4 ppm and 3.6 ppm 

correspond to CH 2 and CH 3 protons of ethoxy 

and methoxy groups, respectively. The CH 3 protons 

of ethoxy groups and those of the backbone rise at 

0.8–2.3 ppm. 

The kinetic study was carried out by 1 H NMR 

spectroscopy. The content of 4 unit in the copolymer 

was calculated from the integral difference 

between the methacrylate methylene protons 

(d = 6.40 ppm and 5.80 ppm) of residual monomer 

4 and protons at d = 8.0–8.3 ppm (CH@C and 

Ar–H 2,6) of both residual monomer 4 and monomer 

4 incorporated in copolymer. For content of MMA 

unit in the copolymer, it was calculated from the 

e 

O 

f h 

4.0 

d 

CH 3 

C 

O 

3.0 

e' 

d' 

CH 3 

CH2 C 

p 

CH2 C 

q 

CO2CH3 h 

2.0 

d,d' ,e,e',g 

Fig. 4. 1 H NMR spectra of 6b recorded at different times of the copolymerization (t = 0, 4, 6 and 8h). 

1.0 

0.0

Table 2 

Molar fractions of 4 in feed (f) and in copolymers (F), and parameters required for calculating monomer reactivity ratios by using 

Finneman–Ross method 

Copolymer f F d[4] d[MMA] Conversion (%) X Y X 2 /Y (Y 1)X/Y 

6a 0.2 0.09 0.07 0.70 3.24 0.25 0.10 0.63 2.25 

6b 0.3 0.16 0.11 0.61 3.87 0.43 0.18 1.02 1.95 

6c 0.5 0.30 0.13 0.30 2.91 1.00 0.43 2.31 1.31 

6d 0.7 0.61 0.34 0.22 5.81 2.33 1.55 3.52 0.82 

6e 0.8 0.70 0.15 0.06 2.68 4.00 2.50 6.40 2.40 

integral difference between the methylmethacrylate 

methylene protons (d = 6.15 ppm and 5.60 ppm) of 

residual MMA and methoxy protons of both residual 

MMA and MMA incorporated in copolymer 

(d = 3.6 ppm)] (Fig. 4). The comonomer (4) composition 

data of feed and copolymers are given in 

Table 2. 

Plot of molar fraction of 4 in copolymers (F) versus 

molar fraction of 4 in the feed (f) (Fig. 5) shows 

that the reactivity of MMA is much higher than that 

of 4 toward both propagating species. 

Monomer reactivity ratios were estimated at low 

conversion (lower than 6%) to satisfy the differential 

copolymerisation equation. They were determined 

using the Finneman–Ross equation [15,16]. According 

to this method the monomer reactivity ratios 

can be obtained by the following equation: 

X 

ðY 1Þ 

Y 

ðX 

¼ r1 

2 Þ 

Y 

r2 

where the ratios reactivity r1 and r2 correspond to 4 

and MMA, respectively, and X, Y are defined as 

follows: 

X ¼½4Š=½MMAŠ and Y ¼ d½4Š=d½MMAŠ 

F 

1.00 

0.80 

0.60 

0.40 

0.20 

0.00 

0 0.2 0.4 0.6 0. 8 1 

Fig. 5. Copolymer composition diagram of poly(4-co-MMA). 


f 

where [4] and [MMA] are the monomer molar compositions 

in feed and d[4] and d[MMA] the copolymer 

molar compositions. 

The parameters used for calculation of the reactivity 

ratios of 4 (r1) andMMA(r2) are provided 

in Table 2. 

The plot of X(Y 1)/Y versus X 2 /Y leads to a 

straight line that allows the determination of r1 

(0.8) and r 2 (2.8) with a correlation coefficient (R) 

of about 0.98 (Fig. 6). Linearity of the plot indicates 

that the copolymerization follows the conventional 

copolymerization kinetics and that the reactivity 

of a growing polymer radical only depends on the 

terminal monomer unit. Furthermore, the fact that 

reactivity ratio of 4 is lower than that of MMA 

(r1 < r2) and the product r1 Æ r2 is higher than 1 

(r 1 Æ r 2 = 2.2), it confirms that the reactivity of 4 is 

much lower than that of MMA. 

3.4. Photoreactivity of the synthesized polymer 

and copolymers 

A first approach of the photoreactivity in solid 

state of the synthesized polymer and copolymers 

was carried out with copolymer 6b. Thin films of 

this copolymer were irradiated using a B100A 

X (Y-1) / Y 

3.00 

2.00 

1.00 

-2.00 

-3.00 

y = 0.8409x - 2.7899 

R 2 = 0.958 

0.00 

0.00 

-1.00 

2.00 

c 

4.00 6.00 8.00 

Y*Y / X 

Fig. 6. Finneman–Ross plot for poly(4-co-MMA).


Ultraviolet lamp. IR and UV spectra of the copolymer 

6b recorded after various times of irradiation 

are given in Fig. 7. The UV analyses show that 

the intensity of absorbance at k = 310 nm due to 

cinnamate moieties decreases during exposure. 

While that at k = 260 nm due to the cyclobutane 

formation increases gradually. The insolubility of 

the studied films in organic solvents after the irradiation 

confirms that photocrosslinking took place. In 

IR analysis, the decrease of C@C absorption band 

at 1613 cm 1 upon irradiation was assigned to the 

cyclobutane formation by dimerization of C@C cinnamate 

groups. 

More detailed studies on the ability of homopolymer 

5 and copolymers 6 to crosslink under UV 

irradiation are under investigation. The results of 

these studies will be reported elsewhere. 

4. Conclusion 

Absorbance 

a b 

1.0 

0.8 

0.6 

0.4 

200 300 400 500 

Wavelength 

- 0 min 






Photosensitive polymers with cinnamate units 

in side position of chains were prepared by homopolymerization 

and copolymerization of ethyl acyano-4-(methacryloxy)cinnamate 

with methyl 

methacrylate. Homopolymerization and copolymerizations 

were carried out at 65 °C in chloroform. 

The structures of the formed polymers were characterized 

by IR and 1 H NMR. Homo- and co-polymers 

of medium molecular weights were obtained 

with good yields (60–95%). They were easily soluble 

in most of the organic solvents such as butanone, 

THF, CH 2Cl 2, CHCl 3, benzene, toluene, DMF 

and dioxane. 

Absorbance 

0.4 

0.3 

0.2 

0.1 

0.0 







1600 1650 1700 1750 

Kinetic studies of homo- and co-polymerization 

were performed in deuterated chloroform under 

nitrogen atmosphere. In the case of the homopolymerization 

of 4, the plot of Ln(M0/Mt) versus 

[1 exp( kd Æ t/2)] leads to a kp= ffiffiffiffi p 

kt ratio value of 

0.04 mol 1/2 l 1/2 s 1/2. By comparing with that 

determined for MMA (kp= ffiffiffiffi p 

kt ¼ 0:12), it was 

deduced that 4 is about three times less reactive than 

MMA. This difference of reactivity between 4 and 

MMA can be explained both by steric hindrance 

and radical resonance stabilization of cinamate unit. 

The lower reactivity of 4 compared with that of 

MMA was confirmed by the results of copolymerizations 

performed between 4 and MMA, more 

especially by reactivity ratios of 4 (r1 = 0.08) and 

MMA (r2 = 2.8) determined from the Finneman– 

Ross method. 

A first test of photoreactivity performed with 6b 

showed that the synthesized polymers can crosslink 

in the solid state when they are exposed to UV 

irradiation. 

The insolubility of the film at the end of the exposure 

to UV irradiation and the disappearance of the 

UV absorbance at k = 310 nm characteristic of the 

cinnamate functions, are significant that crosslinking 

occurred probably according to a mechanism 

similar to that found for cinnamate acid and its 

derivatives [17]. 

Acknowledgement 

Wavelength 

Fig. 7. UV and IR spectra of copolymer 6b (f = 0.3) recorded after each exposure interval. 

The authors thank the ‘‘Comité Mixte Franco- 

Marocain’’ for its financial support through the

national program of research (Action intégrée MA/ 

02/41). 

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