Glass-transition temperatures and rheological behavior of methyl methacrylate–styrene random copolymers

✍ Scribed by Guodong Liu; Liucheng Zhang; Yanmei Yao; Liting Yang; Jungang Gao

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 92 KB
• Volume: 88
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.11891

✦ Synopsis

Abstract

Poly(methyl methacrylate‐ran‐styrene) copolymers were synthesized under monomer‐starved conditions by emulsion copolymerization. The glass‐transition temperatures (T~g~'s) of the copolymers were measured by differential scanning calorimetry (DSC) and torsional braid analysis (TBA). The results showed that the methyl methacrylate–styrene random copolymers produced an asymmetric T~g~ versus composition curve, which could not even be interpreted by the Johnston equation with different contributions of dyads to the T~g~ of the copolymer considered. A new sequence distribution equation concerning different contributions of triads was introduced to predict the copolymer's T~g~. The new equation fit the experimental data exactly. Also, the T~g~ determined by TBA (T~__g__TBA~) was higher than the one determined by DSC (T~__g__DSC~) and the difference was not constant. The rheological behavior of the copolymers was also studied. T~__g__TBA~ − T~__g__DSC~ increased with increasing flow index of the melt of the copolymer, and the reason was interpreted. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2891–2896, 2003