Effect of dangling chains on the structure and physical properties of a tightly crosslinked poly(ethylene glycol) network

Radi, Babak, Wellard, R. Mark, & George, Graeme A. (2013) Effect of dangling chains on the structure and physical properties of a tightly crosslinked poly(ethylene glycol) network. Soft Matter, 9(12), pp. 3262-3271.

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Abstract

Major imperfections in crosslinked polymers include loose or dangling chain ends that lower the crosslink d., thereby reducing elastic recovery and increasing the solvent swelling. These imperfections are hard to detect, quantify and control when the network is initiated by free radical reactions. As an alternative approach, the sol-​gel synthesis of a model poly(ethylene glycol) (PEG-​2000) network is described using controlled amts. of bis- and mono-​triethoxy silyl Pr urethane PEG precursors to give silsesquioxane (SSQ, R-​SiO1.5) structures as crosslink junctions with a controlled no. of dangling chains. The effect of the no. of dangling chains on the structure and connectivity of the dried SSQ networks has been detd. by step-​crystn. differential scanning calorimetry. The role that micelle formation plays in controlling the sol-​gel PEG network connectivity has been studied by dynamic light scattering of the bis- and mono-​triethoxy silyl precursors and the networks have been characterized by 29Si solid state NMR, sol fraction and swelling measurements. These show that the dangling chains will increase the mesh size and water uptake. Compared to other end-​linked PEG hydrogels, the SSQ-​crosslinked networks show a low sol fraction and high connectivity, which reduces solvent swelling, degree of crystallinity and the crystal transition temp. The increased degree of freedom in segment movement on the addn. of dangling chains in the SSQ-​crosslinked network facilitates the packing process in crystn. of the dry network and, in the hydrogel, helps to accommodate more water mols. before reaching equil.

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ID Code: 65245
Item Type: Journal Article
Refereed: Yes
Keywords: poly ethylene glycol, Solid State Magic angle spinning NMR, cross-linking, sol-gel
DOI: 10.1039/c3sm27819k
ISSN: 1744-6848
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > MACROMOLECULAR AND MATERIALS CHEMISTRY (030300)
Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > ORGANIC CHEMISTRY (030500)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > Institutes > Institute for Future Environments
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Funding:
Copyright Owner: Copyright 2013 The Royal Society of Chemistry
Deposited On: 10 Dec 2013 23:09
Last Modified: 15 Apr 2014 14:29

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