Free-Radical Copolymerization I. Reactivity Ratios in Bulk-Copolymerization of p-Chlorostyrene and Methyl Acrylate

Abstract

ABSTRACT:In order to establish the composition equation for the bulk-copolymerization of p-chlorostyrene (monomer I) and methyl acrylate (monomer 2) at 40°C, an extraordinarily large number of careful polymerization runs were carried out covering a wide range of feed composition. The samples were analyzed for composition by both potentiometric titration for chlorine and combustion analysis for carbon. The optimum set of terminal-model parameters evaluated by a least-squares curve-fitting procedure are r 1 = 1.21 and r 2 =0.144, quite at variance with the literature values, but conform to the Q-e scheme. However, the chlorine and carbon sets of data consistently indicate failure of the terminal model to accurately represent this system. The penultimate model parameters r1 =0.92, r1 ' =2.3, and r2 ( =r/)=0.18 represent the system almost perfectly. This indicates the presence of significant penultimate effects on type-! radicals. The question as to the penultimate effects on type-2 radicals remains to be answered.

Free-Radical Copolymerization VII. Reinterpretation of Velocity-of-Copolymerization Data

“…Again, it is indicated that eq 21 and 22 may be reasonable approximations. (As reported previously, 11 the composition curve of the pCS/MA system is better represented by the penultimate model than by the terminal model. Hence, it is expected that better agreement between the calculative and experimental curve and a more accurate value of s will be obtained by removing the approximation of i; = r; = constant that we made in this paper.)…”

“…This equation allows the determination of the cross-termination factor <p without knowing k 11 and k12 • This factor should be close to 1:1nity unless 1 ~2 crossterminations are chemically favored over 1-1 and 2-2 homo-terminations. Values of¢ experimentally determined via eq 1 were often Table II and the text for details).…”

Free-Radical Copolymerization II. Volume Contraction Factors for Some Copolymerization Systems. An Approach Based on Partial Specific Volume

“…The methods of polymerization and purification of the polymers are described elsewhere. 2 The copolymer composition was determined by combustion analysis for carbon. The molecular 674 weights were determined by gel permeation chromatography (GPC).…”

“…The number-average molecular weight Mn and the ratio Mw/ Mn of the weight-to-number average molecular weights of the ST-MMA copolymer were estimated on the assumption that the calibration curve for the copolymer is a composition average of those for the parent polymers, while those of the pCS-MA copolymer were estimated by the method described previously. 2 …”

“…If +x3Fz(a34 V4 + Vt4 -V~,3) (2) with I'i°=V3 -V?, 3 and I'z°=V4 -V~. 4 (3) where the superscript "0" denotes the infinite dilution; x is the volume composition of the monomers before mixing (x3 + x 4 = 1 ), F, the molecomposition of the copolymer (F 1 + F 2 = 1), F 12 , the population of the 1 ~2 chemical bonds, Vt, the partial molar volume (per monomeric unit) of homopolymer i in the pure monomer j, and V3 and V 4 , the molar volumes of the pure monomers.…”