Journal of Polymer Research 10: 21–29, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.
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Synthesis, Characterization and Reactivity Ratios of Phenylethyl Acrylate/Methacrylate Copolymers U. Senthilkumar, Kilivelu Ganesan and B. S. R. Reddy∗ Industrial Chemistry Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India (∗ Author for correspondence; E-mail:
[email protected]) Received 17 May 2002; accepted in revised form 30 September 2002
Key words: 2-Phenylethyl acrylate (PEA), 2-Phenylethyl methacrylate (PEMA), methyl acrylate, N-vinyl pyrollidone, reactivity ratios
Abstract 2-Phenylethyl acrylate (PEA) and 2-Phenylethyl methacrylate (PEMA) were synthesized by reacting 2-Phenyl ethanol with acryloyl and methacryloyl chloride respectively. Homopolymers and copolymers were prepared by free radical polymerization technique using benzoylperoxide as initiator. Copolymers of PEA and PEMA with methyl acrylate (MA) and N-vinyl pyrollidone (NVP) of different compositions were prepared. The monomers and polymers were characterized by IR and NMR techniques. Thermal stability of the polymers were determined by TG analysis. The composition of the copolymer was determined using 1 H-NMR analysis. The reactivity ratios of the monomers were determined by the application of Finemann–Ross and Kelen–Tudos methods. The prepared copolymers were tested on leather for their pressure sensitive adhesive property.
Introduction Copolymerization is one of the important techniques adopted in effecting systematic changes in the properties of the commercially important polymers. The copolymers of acrylic/methacrylic esters have been used for various industrial applications [1, 2]. Phenyl acrylate polymers are relatively newly developed materials compared to the commercial polymers such as vinylics, acylamides, alkylamide, etc. Phenyl acrylates, phenolic esters of acrylic/methacrylic acid are considered as a reactive monomers primarily because of the presence of the aromatic ring [3]. The copolymers based on halogenated phenyl acrylate have been utilized for synthesizing electroactive polymers for the preparation of polymeric reagents carrying piperazine and isonitrile functionalities [4, 5]. Copolymer of chlorophenyl acrylate and methylacrylate was used as base coat for leather [6]. Phenyl acrylate copolymers crosslinked with divinylbenzene are used as polymer supports for pharmacological drugs and in the binding of drugs into synthetic polymers [7, 8]. Methacrylate monomers of 2-carboxyphenol and 4-acetamido phenol and their homopolymers were found to possess anti-pyretic activity [9]. The present work deals with the synthesis and characterization of the monomers, phenylethyl acrylate (PEA) and phenylethyl methacrylate (PEMA) and copolymers (poly(PEA-co-MA), poly(PEMA-co-MA), poly(PEA-coNVP) and poly(PEMA-co-NVP)). The copolymer composition and the reactivity ratio values using Fineman–Ross [10] and Kelen–Tudos [11] methods were determined by
1 H-NMR
analysis. The prepared copolymers were tested for their pressure sensitive adhesive property on leather. Thermal stability of the polymers were also studied.
Experimental Materials Acrylic acid and methacrylic acid purchased from Sigma chemical Co. were used as received without removing the inhibitor for the preparation of acryloyl/methacryloyl chloride. Benzoyl chloride was purchased from BDH. Benzoyl peroxide (Merck) was recrystallized from 1 : 1 mixture of chloroform and ethanol. 2-Phenylethanol (Fluka) was used as such. MA and NVP were distilled at reduced pressure. Fractionally distilled solvents were used in the reaction. Synthesis of Acryloyl Chloride and Methacryloyl Chloride Acryloyl chloride and methacryloyl chloride were prepared by the reported procedure [12]. Synthesis of 2-Phenylethyl Acrylate (PEA) Into a three necked 250 ml round bottom flask equipped with mechanical stirrer, dropping funnel and guard tube, 12.2 ml (0.1 mol) of 2-Phenylethyl alcohol in 50 ml of ethyl methyl ketone (EMK) was taken. 10.1 ml (0.1 mol) of triethylamine was added into the flask and the temperature of the content were maintained at 0–5 ◦C with constant stirring. 9.0 ml
22
U. Senthilkumar et al.
(0.1 mol) of acryloyl chloride in 20 ml of EMK was taken in a dropping funnel and slowly added into the flask. After the addition was completed, the reaction mixture was kept stirring at the same temperature for 1 hour and at room temperature for another 1 hour. The triethylammonium chloride salt, which precipitated out during the reaction was filtered and discarded. The filtrate was washed with 5% NaOH solution, dried with anhydrous ammonium sulphate. The solvent in the filtrate was evaporated and a liquid monomer (PEA) was obtained.
in Tables 1–4. Appropriate quantities of the monomer, comonomer, EMK and BPO were taken in a polymerization tube and flushed with oxygen free nitrogen gas for 15 minutes. The reaction mixture was sealed under nitrogen atmosphere and immersed in a thermostatic water bath at 70 ± 1◦ C. Copolymerization was allowed to proceed to about 15% conversion. The copolymer was precipitated by pouring the reaction mixture into excess methanol. It was filtered and dried in vacuum oven at 40 ◦C.
Synthesis of 2-Phenylethyl Methacrylate (PEMA)
Measurements
2-Phenylethyl methacrylate was synthesized by adopting the same experimental procedure as described above. 12.2 mL (0.12 mol) of 2-Phenylethyl alcohol in 50 mL of EMK and 16.7 mL (0.12 mol) of triethylamine were taken in a 250 mL three neck round bottom flask. Methacryloyl chloride 9.6 mL (0.1 mol), was taken in the dropping funnel. The monomer was obtained in the liquid form.
FT-IR spectra of the monomers and polymers were obtained on Perkin Elmer FT-IR spectrometer. 1 H and 13 C-NMR spectra of the samples were recorded on Bruker NMR spectrophotometer at 300 MHz and 75 MHz respectively. Dueterated dimethylsulfoxide (DMSO-d6) was used as solvent and tetramethylsilane (TMS) served as an internal standard. The measurements of thermal stability of polymers were obtained on Mettler 3000 Thermal analyzer at a heating rate of 10 ◦C/min under nitrogen atmosphere. Peel strength of the prepared copolymers were tested on leather samples using INSTRON, tensile strength testing machine, for their pressure sensitive adhesive property.
Synthesis of Homopolymers of PEA/PEMA About 1 g of PEA/PEMA was placed in a standard tube containing 10 ml of EMK and 50 mg of benzoyl peroxide (BPO). The reaction mixture was flushed with nitrogen gas for 30 minutes, sealed and kept in a thermostat at 70 ±1 ◦ C for 24 h. After allowing the reaction for the required period of time, the homopolymer was precipitated by pouring the reaction mixture into excess methanol. The polymer obtained was filtered and dried under vacuum. Synthesis of Copolymers of PEA/PEMA with MA and NVP Copolymers of PEA/PEMA with MA and NVP having different composition, were synthesized in EMK solution using BPO as a free radical initiator. The feed composition of the monomers and comonomers were given
Results and Discussion Four copolymers, poly(PEA-co-MA), poly(PEA-co-NVP), poly(PEMA-co-MA) and poly(PEMA-co-NVP) were synthesized by taking different mole fraction of the monomers in the feed ranging from 0.1 to 0.9. The copolymers were found to be soluble in chloroform, dimethylformamide, dimethylsulfoxide, tetrahydrofurane and N-methyl-2-pyrrolidone but insoluble in solvents like benzene, toluene, hexane, methanol and ethanol. The monomers and polymers
Table 1. Composition data for Poly(PEA-co-MA) M1
Iaro
Iali
C
m1
% yield
F = M1 /M2
f = m1 /m2
G = F (f − 1)/f
H = F 2 /f
η = G/(α + H ) ξ = H /(α + H )
0.1 0.35 0.50 0.65 0.90
7.43 13.98 8.22 9.87 1.63
56.29 40.03 16.82 17.85 2.59
0.132 0.349 0.489 0.553 0.631
0.163 0.450 0.650 0.746 0.866
7.8 8.1 8.9 11 8.4
0.1111 0.538 1.0 1.857 9.0
0.1947 0.8181 1.8571 2.9370 6.4626
−0.4592 −0.1196 0.4615 1.2247 7.6073
0.0633 0.3538 0.5384 1.1174 12.5336
−0.4816 −0.0961 0.3229 0.5931 0.5666
f = m1 /m2
G = F (f − 1)/f
H = F 2 /f
η = G/(α + H ) ξ = H /(α + H )
0.1614 0.5384 0.7513 1.2675 2.4360
−0.5773 −0.4616 −0.3310 0.3919 5.3054
0.0764 0.5384 1.3310 2.7209 33.250
−0.3456 −0.2165 −0.1132 0.0908 0.1523
0.0663 0.2842 0.3767 0.5686 0.9336
α = (Hmax × Hmin )1/2 . Table 2. Composition data for Poly(PEA-co-NVP) Iali
Iaro
0.1 0.35 0.50 0.65 0.90
17.35 216.87 0.08 0.139 11.4 25.96 123.0 0.211 0.350 8.3 17.59 66.88 0.263 0.429 9.1 19.73 55.57 0.355 0.559 8.9 7.21 15.40 0.468 0.709 10.3
α = (Hmax × Hmin )1/2 .
C
m1
% yield F = M1 /M2
M1
0.1111 0.5384 1.0 1.8571 9.0
0.0457 0.2525 0.4550 0.6306 0.9542
Phenylethyl Acrylate/Methacrylate Copolymers
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Table 3. Composition data for Poly(PEMA-co-MA) M1
Iaro
Iali
C
m1
% yield F = M1 /M2
0.20 11.94 56.32 0.212 0.291 7.8 0.35 8.86 30.47 0.291 0.423 8.4 0.50 6.21 16.21 0.383 0.596 9.3 0.65 9.47 20.49 0.462 0.767 10.4 0.80 3.27 6.49 0.504 0.866 11.2
0.25 0.5384 1.0 1.8571 4.0
f = m1 /m2
G = F (f − 1)/f
H = F 2 /f
η = G/(α + H ) ξ = H /(α + H )
0.4104 0.7331 1.4752 3.2918 6.4627
−0.3592 −0.1960 0.3221 1.2929 3.3810
0.1523 0.3954 0.6779 1.0477 2.4757
−0.4687 −0.1942 0.2493 0.7781 1.0943
0.1987 0.3917 0.5247 0.6305 0.8013
α = (Hmax × Hmin )1/2 . Table 4. Composition data for Poly(PEMA-co-NVP) M1
Iaro
Iali
C
m1
% yield
F = M1 /M2
f = m1 /m2
G = F (f − 1)/f
H = F 2 /f
η = G/(α + H ) ξ = H /(α + H )
0.20 0.35 0.50 0.65 0.80
17.93 19.71 22.66 14.53 2.82
59.76 57.46 50.58 29.71 5.27
0.300 0.343 0.448 0.489 0.535
0.541 0.617 0.807 0.881 0.963
7.6 8.0 9.1 10.2 11.7
0.25 0.538 1.0 1.857 4.0
1.178 1.610 4.181 7.403 26.02
0.037 0.203 0.760 1.606 3.846
0.0538 0.1797 0.2391 0.4658 0.6149
0.1599 0.5614 1.8052 2.4796 4.8269
0.2282 0.4969 0.5676 0.7191 0.7718
α = (Hmax × Hmin )1/2 .
were characterized by IR and NMR techniques and the results were given below. The reaction scheme involved in the synthesis of the monomers (PEA or PEMA) and copolymers were given in Scheme 1 and Scheme 2 respectively.
Scheme 1.
Figure 1. 1 H-NMR spectrum of PEA.
PEA FT-IR (cm−1 ): 3083 (aromatic C–H stretch), 2950 and 2883 (asymmetric and symmetric aliphatic C–H stretch), 1724 (C=O stretch), 1624 (olefinic C=C stretch), 1569 (aromatic C=C stretch) and 699 (aromatic out of plane C–H bending). 1 H-NMR (ppm) (Figure 1): 7.23 (5H, Ar–H), 6.28, 5.90 (2H, CH2 =), 6.11 (1H, –CH=), 4.28 (2H, –CH2 O) and 2.89 (2H, –CH2 –Ar). 13 C-NMR (ppm): 166 (carbonyl carbon), 133–125 (olefinic and aromatic carbon), 64 (methyleneoxy carbon) and 34 (methylene carbon).
Scheme 2.
PEMA FT-IR (cm−1 ): 3092 (aromatic C–H stretch), 2945 and 2880 (asymmetric and symmetric aliphatic C–H stretch), 1722 (C=O stretch), 1626 (olefinic C=C stretch), 1562 (aromatic C=C stretch) and 698 (out of plane C–H bending vibration). 1 H-NMR (ppm) (Figure 2): 7.23 (5H, Ar–H), 5.96, 5.59 (2H, CH2 =), 4.26 (2H, –CH2 O), 2.89 (2H, –CH2 –Ar) and 1.81 (3H, methyl protons). 13 C-NMR (ppm): 166 (carbonyl carbon), 136–123 (olefinic and aromatic carbon), 65 (methyleneoxy carbon), 34 (methylene carbon) and 18 (methyl carbon).
24
U. Senthilkumar et al. in the monomeric units, the mole fraction of the monomer (m1 ) and the comonomer (m2 ) present in the copolymer can be easily determined. In our copolymer systems, the mole fraction of the monomer present in the copolymer were determined by taking the ratio of integrated intensities of aromatic protons to the total aliphatic protons. C= Figure 2. 1 H-NMR spectrum of PEMA.
Poly(PEA-co-MA) FT-IR (cm−1 ): 3076 (aromatic C–H stretch), 2954 and 2879 (asymmetric and symmetric C–H stretch), 1734 (C=O stretch), 1146 (C–O stretch of ester group), 1561 (aromatic C=C stretch) and 696 (aromatic C–H out of plane bending). 1 H-NMR (ppm): 7.24 (5H, Ar–H), 4.12 (2H, –CH O), 2 2.79 (2H, –CH2 –Ar), 2.15 (1H, –CH–), 1.48 (4H, –CH2 – in the backbone) and 3.57 (3H, –OCH3 ). Poly(PEA-co-NVP) FT-IR (cm−1 ): 3084 (aromatic C–H stretch), 2954 and 2885 (asymmetric and symmetric aliphatic C–H stretch), 1568 (aromatic C=C stretch), 1427 (C–N stretch), 1163 (C–O stretch of ester group) and 698 (aromatic C–H out of plane bending). 1 H-NMR (ppm): 7.21 (5H, Ar–H), 4.12 (2H, –CH O), 2 2.81 (2H, –CH2 –Ar), 3.18, 1.94 and 2.18 (methylene protons α, β, γ to the carbonyl group in NVP unit) 2.13 (1H, –CH–) and 1.47 (4H, –CH2 – in the backbone). Poly(PEMA-co-MA) FT-IR (cm−1 ): 3081 (aromatic C–H stretch), 2951 and 2881 (asymmetric and symmetric C–H stretch), 1192 (C–O stretch of ester group), 1729 (C=O stretch), 1561 (aromatic C=C stretch) and 696 (aromatic C–H out of plane bending). 1 H-NMR (ppm): 7.25 (5H, Ar–H), 4.04 (2H, –CH O), 2 2.80 (2H, –CH2 –Ar), 1.82 (1H, –CH), 1.25 (4H, –CH2 – in the backbone) and 0.56 (3H, –CH3 ). Poly(PEMA-co-NVP) FT-IR (cm−1 ): 3079 (aromatic C–H stretch), 2952 and 2885 (asymmetric and symmetric aliphatic C–H stretch), 1728 (C=O stretch), 1563 (aromatic C=C stretch), 1424 (C–N stretch), 1162 (C–O stretch of ester group) and 699 (aromatic C–H out of plane bending). 1 H-NMR (ppm): 7.23 (5H, Ar–H), 4.05 (2H, –CH O), 2 3.57 (3H, –O–CH3 ), 2.84 (2H, –CH2 –Ar), 3.18, 1.94 and 2.18 (methylene protons α, β, γ to the carbonyl group in NVP unit), 1.84 (1H, –CH– backbone) and 1.17 (2H, –CH2 – in the backbone).
Intensities of aromatic protons . Intensities of total aliphatic protons
Aromatic protons give a distinct signal at 7.3 ppm. Since aliphatic protons are present in both monomeric units and the signal produced by different methylene and methine protons were found to overlap with each other, the total intensities of aliphatic proton were taken for calculation. In PEA and PEMA unit, there are 5 aromatic protons present in each, whereas the number of aliphatic proton present in each unit is 7 protons and 9 protons respectively. There are no aromatic protons present in both MA and NVP unit, the number of aliphatic protons present in these units are 6 protons and 9 protons respectively. The mole fraction of the monomers present in the copolymers were determined by the following equations. For Poly(PEA-co-MA) C=
5m1 7m1 + 6m2
or m1 = 6C/(5 − C).
(1)
or m1 = 9C/(5 + 2C).
(2)
For Poly(PEA-co-NVP) C=
5m1 7m1 + 9m2
For Poly(PEMA-co-MA) C=
5m1 9m1 + 6m2
or m1 = 6C/(5 − 3C).
(3)
For Poly(PEMA-co-NVP) C=
5m1 9m1 + 9m2
or
m1 = 9C/5.
(4)
Using the relationship (1) to (4), the mole fraction of the monomers present in the copolymer were determined by measuring the value of C from the NMR spectrum. Tables 1–4 gives the value of C and the corresponding mole fraction of the monomers in the copolymers. The plot of mole fraction of PEA or PEMA in the feed versus that in the copolymer is given is Figure 3. From the plot it is observed that PEMA is more reactive when compared with MA and NVP as the composition of PEMA is always richer in the copolymer composition. But in the case of PEA systems, it is observed that there is a tendency to reach the azeotropic conditions when the composition of PEA reached (M1 = 0.8) with MA and the composition of PEA reached (M1 = 0.34) with NVP.
Copolymer Composition The 1 H-NMR technique is a well established method for the determination of the copolymer composition. By measuring the intensities of the signal produced by the protons present
Reactivity Ratios The type of copolymer formed will be best understood from the value of reactivity ratio of the copolymers. The reactivity
Phenylethyl Acrylate/Methacrylate Copolymers
Figure 3. Plot of molefraction of PEA/PEMA in the feed versus that in the copolymer: (a) Poly(PEA-co-MA); (b) Poly(PEA-co-NVP); (c) Poly(PEMA-co-MA) and (d) Poly(PEMA-co-NVP).
ratios of the monomer and comonomer are computed using Fineman–Ross and Kelen–Tudos methods. The equation involved in the Fineman–Ross method is F (F − 1)/f = (F 2 /f )r1 − r2 , where F is the ratio of mole fraction of monomer 1 (M1 ) to the mole fraction of monomer 2 (M2 ) in the feed, f is the ratio of mole fraction of monomer 1 (m1 ) to the mole fraction of monomer 2 (m2 ) in the copolymer. A plot of F (F − 1)/f against F 2 /f gives a straight line with a slope equal to r1 and intercept equal to r2 . In Kelen–Tudos method, the equation is η = (r1 + r2 /α)ξ − r2 /α,
(a)
25 where η = G/(α + H ), ξ = H /(α + H ), G = F (F − 1)/f , H = F 2 /f and α is the geometric means of the minimum and maximum H values for a set of data. By plotting η against ξ a straight line is obtained which when extrapolated to ξ = 0 and ξ = 1 gives −r2 /α and r1 respectively. The values of G, H , η and ξ for different copolymers were given in Tables 1–4. The F-R plot and K-T plot obtained by linear regression analysis for Poly(PEA-co-MA), Poly(PEA-co-NVP), Poly(PEMA-co-MA) and Poly(PEMA-co-NVP) were given in Figures 4–7 respectively. The r1 and r2 values of the copolymer systems are given in Table 5. In poly(PEA-co-MA), the value of r1 is greater than r2 , which indicates the presence of higher amount of PEA unit in the copolymer. The product of r1 r2 is less than one, which indicate that the system follows a random distribution of monomeric unit. In poly(PEA-co-NVP), the value of r1 is less than r2 . In this system NVP is found to have slightly higher reactivity than PEA. The product of r1 r2 is 0.27 (K-T plot), which is closer to zero than unity. Hence, the distribution of monomeric units in the copolymer is random with a greater tendency to alternation. In poly(PEMA-co-MA), the value of r1 is greater than r2 . PEMA is found to be more reactive than MA. The product of r1 r2 is greater than 1 indicating random distribution of monomers. In poly(PEMA-co-NVP) the value of r1 is very much greater than r2 . PEMA is found to be much more reactive than NVP and the PEMA unit will be richer with the copolymer formed. Thermal Analysis The thermal stability of the polymers were identified by estimating the percentage weight loss of the polymer on thermal decomposition. The decomposition temperature of the copolymer depends on the composition of the constituent monomeric units in the copolymer. The TG and DTG
(b)
Figure 4. (a) F–R plot for Poly(PEA-co-MA); (b) K–T plot for Poly(PEA-co-MA).
26
U. Senthilkumar et al.
(a)
(b)
Figure 5. (a) F–R plot for Poly(PEA-co-NVP); (b) K–T plot for Poly(PEA-co-NVP).
(a)
(b)
Figure 6. (a) F–R plot for Poly(PEMA-co-MA); (b) K–T plot for Poly(PEMA-co-MA).
(a)
(b)
Figure 7. (a) F–R plot for Poly(PEMA-co-NVP); (b) K–T plot for Poly(PEMA-co-NVP).
Phenylethyl Acrylate/Methacrylate Copolymers
27
Table 5. Reactivity ratio values for the copolymers Copolymer
Poly(PEA-co-MA) Poly(PEA-co-NVP) Poly(PEMA-co-MA) Poly(PEMA-co-NVP)
r1
r2
F–R
K–T
F–R
K–T
0.62 ± 0.04 0.17 ± 0.008 1.67 ± 0.10 6.48 ± 1.30
0.85 ± 0.20 0.22 ± 0.04 1.65 ± 0.09 5.26 ± 0.28
0.06 ± 0.25 0.45 ± 0.12 0.69 ± 0.12 0.72 ± 0.47
0.32 ± 0.11 0.56 ± 0.04 0.69 ± 0.10 0.40 ± 0.12
Figure 8. TGA curves for Poly(PEA-co-MA) system.
curves for the copolymers were shown in Figures 8–11 in comparison with the homopolymers [Poly(Phenylethyl acrylate) (HPEA), Poly(Phenylethyl methacrylate) (HPEMA), Poly(methylacrylate) (HMA) and Poly(N-vinyl pyrollidone) (HNVP)]. The initial decomposition temperature (IDT) of the methylacrylate copolymer, Poly(PEA-co-MA) and poly(PEMA-co-MA), were found to be higher than the N-vinyl pyrollidone copolymer, Poly(PEA-co-NVP) and Poly(PEMA-co-NVP). It is also observed that the IDT of PEA copolymer is relatively higher than PEMA copolymer. The copolymer prepared with MA, Poly(PEA-coMA) and Poly(PEMA-co-MA), undergoes single stage decomposition whereas the copolymer prepared with NVP, Poly(PEA-co-NVP) and Poly(PEMA-co-NVP), undergoes two stage decomposition. The thermal stability of methylacrylate copolymer was high due to the incorporation of MA in the copolymer systems. The glass transition temperature of the copolymers were determined by differential scanning calorimetry with a Du Pont micro-thermobalance. The Tg values were determined for a particular feed composition (50 : 50) and the results were given in Table 6. The Tg value for the copolymers having phenyl ethyl acrylate as comonomer were low compare
Figure 9. TGA curves for Poly(PEA-co-NVP) system.
Figure 10. TGA curves for Poly(PEMA-co-MA) system.
28
U. Senthilkumar et al. polymers were > 2. The theoretical value of Mw /Mn for polymers produced via radical recombination and radical disproportionation are 1.5 and 2.0 respectively [13]. The value of Mw /Mn > 2 for the copolymer suggests that there is a tendency for radical disproportionation to terminate the polymer chains. Pressure Sensitive Adhesive (PSA)
Figure 11. TGA curves for Poly(PEMA-co-NVP) system.
to the copolymers having phenyl ethyl methacrylate in the copolymers. Molecular Weight The number- and weight-average molecular weights of copolymers with 50 : 50 feed composition were determined by gel permeation chromatography with tetrahydrofuran as an eluent. The molecular data for the four copolymers were given in Table 6. The polydispersity (Mw /Mn ) of these
Many acrylic copolymer shows good adhesive property. Generally pressure sensitive adhesive is a blend of polymer and tackifier. The extent of miscibility of the polymer with the tackifier is important for the application as pressure sensitive adhesive. Many researches have studied the miscibility in acrylic PSA or acrylic copolymer/tackifier systems [14– 16]. In many acrylic PSA it is not necessary to involve any tackifier for most application because a variety of molecular design is possible in this category of materials. The homoand co-polymer prepared were tested for their PSA property on leather without the addition of any tackifier. The prepared copolymer were found to have very good tackiness and they were applied as 40% solution in chloroform on the glossy side of the leather samples and tested for their pressure sensitive adhesive property. The peel strength of the copolymer with different compositions in the feed were given in Table 7. In all the four copolymer systems, the peel strength value was found to increase up to a particular composition and thereafter it was found to decreases. The copolymers of different composition were found to have high peel strength compare to the individual homopolymers. The phenyl acrylate copolymers prepared with methylacrylate, which has low Tg value, was found to have better peel strength compared to the one prepared with NVP monomer.
Table 6. Molecular weight and glass transition temperature Copolymer (composition) Poly(PEA-co-MA) (0.65 : 0.35) Poly(PEA-co-NVP) (0.43 : 0.57) Poly(PEMA-co-MA) (0.60 : 0.40) Poly(PEMA-co-NVP) (0.81 : 0.19)
Tg ◦ C
Molecular weight Mw × 10−4
Mn × 10−4
Mw /Mn
9.50
4.13
2.3
19
5.98
2.26
2.6
24
10.15
4.20
2.4
30
6.80
2.68
2.5
56
Table 7. Peel strength data at different feed composition Polymer
Poly(PEA-co-MA) Poly(PEA-co-NVP) Poly(PEMA-co-MA) Poly(PEMA-co-NVP)
Peel strength (N/mm) at different feed composition 0 : 100
35 : 65
50 : 50
65 : 35
100 : 0
0.80 0.14 0.80 0.14
0.72 0.26 0.91 0.18
1.03 0.42 0.75 0.35
0.57 0.46 0.17 0.25
0.29 0.29 0.12 0.12
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