The glass transition of mixtures of polystyrene with alkyl-terminated oligostyrene — experimental evidence for microphase separation in a polymer blend

✍ Scribed by Volker Abetz; Gunther Müller; Reimund Stadler; Shulamith Schlick

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 604 KB
• Volume: 196
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.1995.021961134

✦ Synopsis

Abstract

Mixtures of high molecular weight polystyrene (P~n~ = 961.5; T~g~ = 373 K) and __sec‐__butyl‐terminated oligostyrene (P~n~ = 10.6; T~g~ = 302 K) show a dependence of the glass transition on the composition (i.e. number‐average molecular weight) which cannot be described by the classic equations of Fox & Flory or Kanig & Ueberreiter. Addition of small amounts of the oligostyrene strongly decreases the glass transition, and above an oligomer content of 40 wt.‐% the glass transition remains constant within experimental error. This behavior can be attributed to the unfavorable interactions between the alkyl‐terminated oligomer and the high molecular weight PS. As a result the oligomer is a bad solvent but — according to the requirements defined by Kanig — an efficient plasticizer. This behaviour is even more pronounced in mixtures of the alkyl‐terminated oligostyrene with a poly(styrene‐co‐maleic anhydride) of low maleic anhydride content. In this case, ESR spectra of the spin‐labelled styrene copolymer demonstrate the existence of microheterogeneities on the 2–5 nm scale. The findings are in qualitative agreement with recent theoretical work of Khokhlov & Erukhimovich on entropy‐induced microphase separation in blends.