Structure–property relationships in copolymers to composites: Molecular interpretation of the glass transition phenomenon

Abstract

Abstract Structure is taken as the main theme in outlining the mechanical properties of polymer composites. Examples of two‐component polymer systems are selected from the literature showing their morphology, as evidenced from electron micrographs, and their corresponding mechanical properties, as evidenced by dynamic mechanical spectra. A compatibility number, N c , is defined in a continuous scheme from a compatible system (one glass transition, N c → ∞) to an incompatible system (two glass transitions, N c → 0). The point at which semicompatibility occurs, N c ≅ 1, is taken as the approximate universal segmental length associated with a glass transition. This length of 150 Å allows for 100 to 5000 CC bonds for an associated glass transition. The ramifications of this molecular interpretation of a glass transition are discussed, resulting in a denouncement of the time–temperature correspondence principle and a new interpretation of short‐segmental block copolymers.