Influence of crosslinking functionality, temperature and conversion on heterogeneities in polymer networks

DM Kroll and SG Croll, POLYMER, 79, 82-90 (2015).

DOI: 10.1016/j.polymer.2015.10.020

Crosslinked polymer formation commonly occurs when two or more multi- functional precursors react to form a three-dimensional network. The resulting networks may contain a significant number of topological imperfections such as loops or dangling ends when formed using crosslinkers with high functionality or when crosslinking at high temperatures. We employ molecular dynamics simulations to analyze these topological imperfections in coarse-grained networks generated from precursors consisting of 'chain extenders' composed of two beads (dimers) and a crosslinker of functionality f = 3 or 6 for a wide range of crosslinking temperatures and final conversions. It is shown that these imperfections result in networks in which the number of elastically active chains, the cycle rank and the number of elastically active junctions is smaller than predicted by the Miller-Macosko theory. Such defects must adversely affect the mechanical properties, resistance to solvent swelling and, possibly, the long-term protective properties of polymer networks. (C) 2015 Elsevier Ltd. All rights reserved.

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