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Investigating the Free‐Volume Characteristics of Regulated Dimethacrylate Networks Below and Above Glass Transition Temperature
Author(s) -
Švajdlenková Helena,
Šauša Ondrej,
Mat́ko Igor,
Koch Thomas,
Gorsche Christian
Publication year - 2018
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201800119
Subject(s) - glass transition , differential scanning calorimetry , materials science , polymer , volume (thermodynamics) , polymer chemistry , volume fraction , atmospheric temperature range , thermomechanical analysis , thermal expansion , thermodynamics , composite material , physics
Abstract Studying the relationship between microstructural interactions and resulting macroscopic material properties gives a more elaborate understanding on final material performance. The microstructural arrangement with characteristic length, relaxation, and thermal expansion behavior of regulated dimethacrylate networks is studied by differential scanning calorimetry, dynamic mechanical analysis, thermomechanical analysis, and positron annihilation lifetime spectroscopy at a broad temperature range (250–380 K). The length scale ξ ( T g ) of cooperative segmental rearrangement is decreased with increasing crosslinking and degree of freedom in regulated chain transfer agent (CTA)‐based networks. The macro and microscopic thermal expansion coefficients are determined in the glassy and rubbery state for three polymer systems—a dimethacrylate‐based reference (poly2M) and regulated photopolymers with CTAs (i.e., thiol, β‐allyl sulfone). The influence of CTAs on the free volume characteristics (i.e., free volume void size, the specific occupied volume V 0 , free volume number density per unit mass N ′, and free volume fraction f ) at the glass transition temperature T g is correlated with the cooperative length, activation energy E a, α , and mechanically effective crosslinking density. A more complex understanding of the revealed relations contributes to a more elaborate explanation of final material performance.