PEO-containing copolymers as polyurethane soft segments in the development of high performance materials

Silk-inspired segmented polyurethanes containing flexible, hydrophilic segments with crystalline and liquid crystalline moieties were developed to mimic the hierarchical morphology of the continuous domain in and the superior mechanical properties of native spider silk. A series of polyurethane elastomers were designed with varying poly(ethylene oxide) (PEO)-containing soft segment lengths and hard segment contents. The incorporation of a hydrophobic poly(propylene oxide) (PPO) block and longer soft segment lengths (1900 g/mol) induced a higher degree of micro-phase segregation compared to PEO (1000 g/mol) soft segment polyurethanes of similar hard segment content. Segmented polyurethanes with longer PEO soft segment lengths (4600 g/mol) exhibited a lamellar morphology, which was driven by the high level of crystallinity in both the hard and soft domains. As the hard segment content (26 - 47 wt%) was increased, the crystallinity of the hard domains was enhanced, yielding a shift in the morphology of the continuous domain from soft segment continuous to hard segment continuous or an interconnected microstructure. The mechanical behavior of these systems was affected by the continuous domain morphology. Hysteresis and initial moduli increased, and extensibility decreased as the hard segment size was varied from 26 to 47 wt% in the PEO-PPO-PEO-containing polyurethanes. The pure PEO (1000 g/mol) soft segment polyurethane exhibited enhanced extensibility, tensile strength, and toughness compared to the PEO-PPO-PEO segmented polyurethanes, which was attributed to the presence of load-bearing crystallites.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• James-Korley, LaShanda Teresa

Advisor dc:contributor.advisor

• Paula T. Hammond and Gareth H. McKinely.

• Chemical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/32319

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/32319