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PEG-POSS Hybrid Polyurethanes: Mechanically Robust Nanostructured Hydrogels

Published online by Cambridge University Press:  01 February 2011

Jian Wu
Affiliation:
wujian@mail.pse.umass.edu, University of Connecticut, Chemical Engineering Department,Polymer Program, Institute of Materials Science, 97 North Eagleville Road, Storrs, CT, 06269, United States
Qing Ge
Affiliation:
Qing@tyrxpharma.com, University of Connecticut, Chemical Engineering Department,and Polymer Program,Institute of Materials Sciece, Storrs, CT, 06269, United States
Patrick T Mather
Affiliation:
ptmather@syr.edu, University of Connecticut, Chemical Engineering Department,and Polymer Program,Institute of Materials Sciece, Storrs, CT, 06269, United States
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Abstract

A series of unique hybrid thermoplastic polyurethanes (TPUs) was synthesized using PEG as soft segment and incorporating an isobutyl-functionalized POSS diol (TMP POSS diol) in the hard segment. The molecular weight of PEG was systematically varied to include 10, 20, and 35 kDa, while the mole ratio of POSS diol (as chain extender) to PEG was in range from 3:1 to 8:1 with samples featuring a PEG molecular weight of 10 kDa. The diisocyanate employed for TPU polymerization was 4,4'-methylenebis(phenyl-isocyanate) (MDI). We found that the hydrophobic hard segments (POSS) can form crystalline structures driven by micro-phase separation, this being due to significant thermodynamic incompatibility between POSS and ethylene oxide units. The POSS nano-crystals thus formed serve as physical crosslinking sites within an inorganic-organic hybrid network. This affords a new hybrid organic-inorganic hydrogel in the water-swollen state. The equilibrium swelling ratio increased monotonically with PEG loading and ranged from ∼70% to ∼600%. The shear modulus, G, of the hybrid hydrogels was observed to span 0.3 < G < 4.0 MPa – C values commonly found for elastomers, not hydrogels. Indeed, the hydrogel stiffness can be finely tuned through the POSS:PEG molar ratio, as this predictably controls swelling in water.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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