Functional monomers and polymers have received considerable attention in recent years, especially in the biomedical field. In this respect, poly(viny1ene carbonate) is very interesting, because the reactive carbonate groups offer the possibility of coupling with bioactive compounds containing amino groups, e. g. proteins or enzymes. Copolymerization of vinylene carbonate with other vinyl monomers will affect the amount of carbonate groups as well as other properties of the copolymers. In a previous paper we described the preparation and properties of poly(viny1ene carbonate) I), and this paper reports the copolymerization of vinylene carbonate with N-vinyl-2-pyrrolidone and with ethyl vinyl ether

Bantjes, Adriaan

Chen, Guohua

Does, Leen van der

Tijsma, Edze Jan

English

van der Does, Leen

NARCIS 

Investigations on vinylene carbonate, 2. Copolymerization with N-vinyl-2-pyrrolidone and ethyl vinyl ether

University of Twente Research Information

Makromol. Chem., Rapid Commun. 11, 501-506 (1990) 501 Investigations on vinylene carbonate, 2 a) Copolymerization with N-vinyl-2-pyrrolidone and ethyl vinyl ether Edze Jan Tijsma, Guohua Chen, Leen van der Does*, Adriaan Bantjes Department of Chemical Technology, Biomaterials Section, Twente University of Technology, P.O. Box 217, 7500 AE, Enschede, The Netherlands (Date of receipt: March 16, 1990) Introduction Functional monomers and polymers have received considerable attention in recent years, especially in the biomedical field. In this respect, poly(viny1ene carbonate) is very interesting, because the reactive carbonate groups offer the possibility of coupling with bioactive compounds containing amino groups, e. g. proteins or enzymes. Copolymeri- zation of vinylene carbonate with other vinyl monomers will affect the amount of carbonate groups as well as other properties of the copolymers. In a previous paper we described the preparation and properties of poly(viny1ene carbonate) I) ,  and this paper reports the copolymerization of vinylene carbonate with N-vinyl-2-pyrrolidone and with ethyl vinyl ether. Radical copolymerization of vinylene carbonate (VCA) was first reported by Price and Padbury’). Several investigations on copolymerization of VCA with vinyl mono- mers were carried out, and in some cases the monomer reactivity ratios were deter- mined3s4). Copolymers of VCA (1) with vinyl compounds (2) in general contain only small amounts of VCA (r,  c 1 and r2 > 1) and show more or less characteristics of an ideal copolymerization (rl = l /r2).  The radical copolymerization of VCA with isobutyl vinyl ether, on the other hand, leads to predominantly alternating copoly- mers’). However, in all these copolymerizations a relatively low reactivity of VCA was observed, due to the 1,Zdisubstitution of the vinylene group. Hayashi and &nets3) already studied the copolymerization of VCA (1) with N- vinyl-2-pyrrolidone (2), and they reported for the reactivity ratios: r ,  = 0,4 and r2 = 0,7, which means that, e. g. with 90 mol-Vo of VCA in the feed, an instantaneous copolymer composition of 80 mol-Vo VCA could be obtained. Because we were interested in high-molecular-weight copolymers containing high amounts of VCA, since this kind of materials might be interesting in biomedical applications (e. g. when grafted on polymeric surfaces), and because poly(N-vinyl-2-pyrrolidone) is known to be a good biocompatible polymer, copolymerization of VCA with N-vinyl-2-pyrroli- done (NVP) was studied. In addition to NVP, being a hydrophilic monomer, the less hydrophilic ethyl vinyl ether (EVE) was copolymerized with VCA, in order to study the a) Part I :  cf. ref. ’) 0 1990, Hiithig & Wepf Verlag, Base1 CCC 01 73-2803/90/$01 .OO 502 E. J. Tijsma, G. Chen, L. van der Does, A. Bantjes effect of the difference in hydrophilicity on the properties of the copolymer and the influence of EVE on the arrangement of the monomeric units along the polymer chain. Experimental part Materials. N-vinyl-2-pyrrolidone (NVP; Merck, Darmstadt, West Germany) and ethyl vinyl ether (EVE; Merck, Darmstadt, West Germany) were purified by distillation. Vinylene carbonate (VCA) was prepared according to a modification of the synthesis from ethylene carbonate as described previously6*7). 2,2'-Azoisobutyronitrile (AIBN J. T. Baker, Deventer, The Nether- lands) and tert-butyl peroxypivalate (Trigonox 25 - 75 C; AKZO, Deventer, The Netherlands) were used as received. Acetone (Merck, Darmstadt, West Germany), used as a solvent in the polymeriza- tion reactions, was distilled before use. Non-solvents, used for precipitating the copolymers, were of analytical grade. Methods: Copolymers from VCA with NVP were obtained by solution polymerization in ace- tone at 50°C for 72 h in the presence of 0,25 mol-% of AlBN. Different amounts of both monomers were dissolved in acetone in thick-walled glass tubes, and after adding the initiator, the tube contents were degassed by freezing in liquid nitrogen and evacuating (3-4 times). After cooling the last time, the tubes were evacuated, sealed, and the polymerization was carried out by heating the tubes in an oil bath. The resulting products were precipitated in an excess of non- solvent (diethyl ether or ethyl acetate), filtered through a glass filter, washed several times, and dried in an oven at 40 "C i. vac. for one night. Solution polymerization of VCA with EVE was performed in acetone ([VCA] + [EVE] = 20 mol/L) at 50°C with 0,25 mol-% of tert-butyl peroxypivalate, according to the procedure described above. The copolymers produced were precipitated in an excess of diethyl ether. Overall conversions were kept low and never exceeded 15 wt.-070. Copolymer compositions were calculated from 'H NMR spectra recorded on a 200 MHz Nicolet NMR spectrometer (DMSO-d, as a solvent) and/or by elemental analysis (C, H or N). Viscometric measurements were carried out with solutions of poly(VCA-co-NVP) in freshly distilled N, N-dimethylformamide, using an Ubbelohde-type viscometer at  25 "C. Limiting viscosity numbers [q] were evaluated by extrapolation to zero concentration (concentration range 1 - 5 mg/mL) '). Results and discussion POIY(VCA-CQ-NVP) Some characteristics of the synthesized VCA-NVP copolymers are listed in Tabs. 1 and 2. From Etb. 1 it can be seen that increasing the monomer feed concentration resulted in a marked increase in the limiting viscosity numbers, [q] .  The effect of monomer feed composition upon the copolymerization is shown in Tab. 2. From the data shown in Tabs. 1 and 2, it can be concluded that copolymerization of VCA with NVP resulted in copolymers with substantial amounts of VCA, depending on the reaction conditions. However, copolymers with higher contents of VCA were not obtained, and we therefore decided to reconsider the r-values, as given by Hayashi and Smets3) (r,  = 0,4 and r2 = 0,7). In doing so, our attention was attracted by the fact that the azeotropic composition Fl ,  AZ, as suggested in their copolymerization diagram, conflicted with the azeotropic composition calculated from the reactivity ratios given by Hayashi and Smets: Fl,AZ = (1 - r2)/(2 - rl - r2) = 0,33. This is best illustrated by Fig. 1 in which both the experimental data of Hayashi and Smets and the curve corresponding to r ,  = 0,4 and r2 = 0,7 are plotted. Hayashi and Smets lnvestigations on vinylene carbonate, 2 503 ,- 0.8 - 0.6 - 0.1 - Tab. 1. Effect of monomer feed concentration upon the copolymerization of vinylene carbonate (VCA) (1) with N-vinyl-2-pyrrolidone (NVP) (2) a) Experiment number 1 2 3 4 Mass of VCA in g Mass of NVP in g ([VCA] + [NVP])/(mol/L) Yield of copolymer in g F, b, Conversion of VCA in Vo [q]/(dL * g-')') in wt.-Vo 4,27 5,70 10 6,92 0,32 0,73 69 43 4,36 538 8,@3 0,37 1,82 20 80 57 4,32 5,62 7,94 0,36 2,05 30 80 56 4,68 5,97 8,62 0,39 2.39 54 81 61 a) Mole fraction of VCA in the monomer feedf, = 0,50. b, Mole fraction of VCA in the copolymer, determined via elemental analysis. ') Determined in N,N-dimethylformamide at 25 "C. Tab. 2. (VCA) (1) with N-vinyl-2-pyrrolidone (NVP) (2)a) Effect of monomer feed composition upon the copolymerization of vinylene carbonate Mass of VCA in g Mass of NVP in g Yield of copolymer in g F, ') Conversion of VCA in Vo [q]/(dL. g-')d) f, b, in wt.-Vo 5 0,84 4,45 0,20 3,78 0,20 1,28 71 73 6 - 1.28 3,92 0,30 3,98 0,09 1 A4 77 22 Experiment number 7 2 8 9 1,77 4,36 3,60 5,58 0,39 0,50 4,46 8,OO 0,18 0,37 1,68 1,82 83 80 37 57 2,58 3 9  2,22 1,11 0.60 0,80 3,43 3,16 O M  0.64 1,45 1.03 71 69 50 53 a) [VCA] + [NVP] = 20moVL. b, Mole fraction of VCA in the monomer feed. ') Mole fraction of VCA in the copolymer, determined via elemental analysis. d, Determined in N,N-dimethylformamide at 25 "C. Fig. 1. poly(VCA-co-NVP), F,, vs. mole fraction of VCA in the monomer feed, f,. x : Experimental data by Hayashi and Smets 3); -: Curve based on r ,  = 0.4 and r2 = 0,7 Mole fraction of VCA (1) in 10 I o,2E n 0 0.2 /I 0.L 0.6 0.8 1.0 504 E. J. Tijsma, G. Chen, L. van der Does, A. Bantjes calculated the reactivity ratios by using the copolymer composition equation. However, after a trial and error procedure with their data and this equation, we found for the reactivity ratios rl = 0,OS and r2 = 1. These recalculated r-values are in agreement with the values more recently reported by Greenley9): rl = 0,055 and r2 = 1,082. When applying the method of Kelen and Tud6s lo) (KT-method) to the data of Hayashi and Smets, we calculated the r-values as rl = 0,Ol and r2 = 0,94. Although Greenley also calculated the r-values from the data of Hayashi and Smets using the KT-method, still some deviation occurs from the r-values we calculated, which may be explained by the fact that the KT-curve did not show a good fit with the experimental data of Hayashi and Smets (regression coefficient = 0,90). More accurate r-values can only be obtained by using more experimental data over a wider range of monomer feed compositions than Hayashi and Smets used. Poly(VCA-CO-EVE) The results of the copolymerizations of VCA with EVE are listed in Tab. 3. The reactivity ratios for the VCA-EVE system were deduced from the composition data derived from the NMR-spectra (using the data from all samples except from experiment 12 because of the deviation between the F,-values from NMR-data and from carbon content determination via elemental analysis) by two graphical methods, according to Fineman and Ross (FR) I ' ) ,  and Kelen and Tiidds b). The monomer reactivity ratios deduced from the plots based on these two methods are presented in 'kb. 4. From this table it can be shown that both methods lead to about Tab. 3. Copolymeriation of vinylene carbonate (VCA) (1) with ethyl vinyl ether (EVE) (2) a) (for explanation of symbols see Tab. 2) Experiment number 10 11 12 13 14 15 16 Mass of VCA in g Mass of EVE in g kield of copolymer in g C-content in Vo H-content in Vo F1 b, F, fvcA d, (after polymerization) Conversion of VCA in Vo Conversion of EVE in Vo f l  in wt.-Vo 0,88 6,48 0.10 0,60 8,2 58,2 8,3 0,27 0,30 0909 20,9 6 4  1,73 5,75 0,20 1 9 0 4  13,9 56,l 7 s  0,37 0,38 0,17 24.8 10.6 2,60 5,07 0,30 0,55 7 2  53,4 6.8 0,40 0,49 0,29 9,4 6.0 3946 4,32 0,40 0,61 7.8 54,O 6.9 0.46 0,47 0,40 8 3  7.0 4,30 3,60 0,50 0,47 599 53,l 6 4  0,49 0,50 0,50 5 3  6.0 604 2,16 0,70 0,55 6 7  51,4 5,9 0,54 0,57 0,7 1 593 10.6 a) [VCA] + [EVE] = 20mol/L. b, Calculated from NMR data. Calculated from C-content determination via elemental analysis. d, Calculated from the initial amount of VCA minus amount of VCA in the copolymer. 7,81 0,76 0 9  0,89 10.4 48,6 5 ,O 0,67 0.69 0,92 8 J  34.2 Investigations on vinylene carbonate, 2 505 Tab. 4. vinyl ether (2) Reactivity ratios r ,  and r2 for the copolymerization of vinylene carbonate (1) with ethyl Calculation method 1 1  r2 Regression coefficient Fineman-Ross-1 Fineman-Ross-2 a) KelenTiidBs 0,12 0,13 0,ll 0,19 0,19 0,19 a) Based on two different Fineman-Ross equations, given in ref. ‘ I ) .  Fig. 2. poly(VCA-co-EVE), F,, vs. mole fraction of VCA in the monomer feed, f l  (curve based on rl = 0,ll and r2 = 0,19) Mole fraction of VCA (1) in the same results. Although there was no considerable deviation between the corresponding r-values derived from two different FR-equations, which is usually the case, because the experimental data are unequally weighted by the FR-equations, the reactivity ratios as calculated with the KT-method were used in further calculations. The copolymer composition curve, calculated with rl = 0,li and rz = 0,19, is shown in Fig. 2, along with the experimental data. It should be noted that in our calculation of the reactivity ratios the initial, instead of the average monomer feed ratio was used, which is not recommended by some authors because of the error intro- duced 12). However, recalculation of the monomer reactivity ratios with the KT- method using the average monomer feed ratio resulted in only relatively small deviations in the r-values: rl = 0,11 and r2 = 0,17. It can be demonstrated, e.g. by calculating diad and triad fractions using the nomograph of Izu and O’Driscoll 1 3 )  that VCA-EVE copolymers have predominantly alternating structure, because fractions of alternating diads and triads exceed 0,80 and 0,65, respectively, for a wide range of monomer feed compositions (fromfl = 0,30 to f, = 0,70). This behaviour of VCA in the polymerization with EVE is in agreement with previously reported data on the copolymerization of VCA with another vinyl ether, viz. isobutyl vinyl ether 5 ) .  506 E. J. Tijsma, G. Chen, L. van der Does, A. Bantjes Conclusions Solution polymerization in acetone at 50 "C in the presence of 2,2'-azoisobutyro- nitrile is a suitable route for the synthesis of high-molecular-weight VCA-NVP copoly- mers. Reconsidering the work of Hayashi and Smets, it appeared that the curve in their copolymerization diagram is not in accordance with the reported r-values. Based on our recalculations, it can only be concluded that the copolymerization of VCA (1) with NVP (2) meets the general rule for copolymerizations of VCA with more reactive vinyl compounds: r ,  < 1 and r2 > 1 .  From the reactivity ratios for the copolymerization of VCA (1) with EVE (2) (r,  = 0,ll and r2 = 0,19) it is clear that the copolymers show an increasing tendency towards alternation as well as they contain relatively larger amounts of VCA compared with other copolymers of VCA. The authors wish to thank Mr. G. J.  Rotscheid of the section for elemental analysis of TNO (Zeist, The Netherlands) for carrying out the elemental analyses. ') J. X. Huang, G. H. Chen, E. J. Tijsma, L. van der Does, A. Bantjes, Chin. J.  Polym. Sci., in 2, U.S. 2 722 525 (1955), American Cyanamid Company, invs.: J. A. Price, J. I. Padbury; Chem. 3, K. Hayashi, G. Smets, J.  Polym. Sci. 27, 275 (1958) 4, J. M. Judge, C. C. Price, J.  Polym. Sci. 41, 435 (1959) ') R. C. Schulz, R. Wolf, Kolloid Z. Z. Polym. 220, 148 (1967) ') N. D. Field, J. R. Schaefgen, J.  Polym. Sci. 58, 533 (1962) 7, M. S. Newman, R. W. Addor, J.  Am. Chem. SOC. 75, 1263 (1953) ') J. F. Rabek, TxperimentaIMethods in Polymer Chemistry': John Wiley & Sons, Chichester- ') R. 2. Greenley, J. Macromol. Sci., Chem. A14, 445 (1980) lo) T. Kelen, F. Tiidds, J .  Macromol. Sci, Chem. A9, 1 (1975) ") M. Fineman, S. Ross, J .  Polym. Sci. 5, 259 (1950) 12) F. L. M. Hautus, H. N. Linssen, A. L. German, J.  Polym. Sci., Polym. Chem. Ed. 22, 3487 '3) M. Izu, K. F. O'Driscoll, J. Appl. Polym. Sci. 14, 1515 (1970) press Abstr. 50, 3011 h (1956) Toronto 1980, p. 127 (1 984) 

Investigations on vinylene carbonate, 2. Copolymerization with N-vinyl-2-pyrrolidone and ethyl vinyl ether

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