Search for a Steric Penultimate Effect: Copolymerization of 2,3,4-Trimethyl-3-pentyl Methacrylate with Styrene
作者:
ThaneD. Rounsefell,
CharlesU. Pittman,
期刊:
Journal of Macromolecular Science: Part A - Chemistry
(Taylor Available online 1979)
卷期:
Volume 13,
issue 2
页码: 153-167
ISSN:0022-233X
年代: 1979
DOI:10.1080/00222337908066593
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
The hindered monomer, 2,3,4-trimethyl-3-pentyl methacrylate (I), was synthesized for penultimate effect studies. Since it readily homopoiymerized (km111≠ 0) and readily copolymerized with styrene, copolymerizations of I with styrene were carried out at 60°C in benzene with AIBN as initiator. The conversion to copolymer and the copolymer composition were determined by using GLC techniques. Composition-conversion data was analyzed by performing a computerized nonlinear least-squares fitting to the integrated form of the penultimate model equation. The experimental design included the use of optimized M1°/M2° ratios. The penultimate reactivity ratios calculated from these data were r1′ = 0.23, r1′= 0.59, r2= 0.59, r2′ = 1.34. Thus, when I is the penultimate unit, a terminal styryl radical prefers to add styrene, whereas when styrene is the penultimate unit, terminal styryl radicals prefer to add I. These results constitute the best evidence for a steric penultimate effect yet available in the literature from composition-conversion studies. However, the case is not yet proved. Further studies to strengthen this conclusion are proposed.
点击下载:
PDF (718KB)
返 回