Utilizing Peptidic Ordering in the Design of Hierarchical Polyurethane/Ureas

Abstract

One of the key design components of nature is the utilization of hierarchical arrangements to fabricate materials with outstanding mechanical properties. Employing the concept of hierarchy, a new class of segmented polyurethane/ureas (PUUs) was synthesized containing either a peptidic, triblock soft segment, or an amorphous, nonpeptidic homoblock block soft segment with either an amorphous or a crystalline hard segment to investigate the effects of bioinspired, multiple levels of organization on thermal and mechanical properties. The peptidic soft segment was composed of poly(benzyl-l-glutamate)-block-poly(dimethylsiloxane)-block-poly(benzyl-l-glutamate) (PBLG-b-PDMS-b-PBLG), restricted to the β-sheet conformation by limiting the peptide segment length to <10 residues, whereas the amorphous soft segment was poly(dimethylsiloxane) (PDMS). The hard segment consisted of either 1,6-hexamethylene diisocyanate (crystalline) or isophorone diisocyanate (amorphous) and chain extended with 1,4-butanediol. Thermal and morphological characterization indicated microphase separation in these hierarchically assembled PUUs; furthermore, inclusion of the peptidic segment significantly increased the average long spacing between domains, whereas the peptide domain retained its β-sheet conformation regardless of the hard segment chemistry. Mechanical analysis revealed an enhanced dynamic modulus for the peptidic polymers over a broader temperature range as compared with the nonpeptidic PUUs as well as an over three-fold increase in tensile modulus. However, the elongation-at-break was dramatically reduced, which was attributed to a shift from a flexible, continuous domain morphology to a rigid, continuous matrix in which the peptide, in conjunction with the hard segment, acts as a stiff reinforcing element.

Silk‐inspired polyurethane containing GlyAlaGlyAla tetrapeptide. II. physical properties and structure

“…26 Korley et al utilized peptidic ordering to design hierarchical polyurethane/ureas. 27 All-non-protein materials have been adopted to synthesize silklike biomaterials. Hammond et al produced a series of silk-like PUs containing poly(ethylene oxide) (PEO) soft segments and 1,6-hexamethylene diisocyanate-1,4-butanediol (HDI-BDO) hard segments (without any peptide links), in which PEO soft segments were semicrystalline and reinforced the PU matrix.…”

Morphology and Mechanical Properties of Thermoplastic Polyurethanes Containing Polyisobutylene/Poly(tetramethylene oxide) Mixed Segments

“…As can be seen from Figure 3, all the samples show endothermic peaks around 150-170 C, which is close to the melting point of the HS based on HDI and BDO (22)(23)(24)(25). The corresponding XRD profiles ( Figure 6) also show diffraction peaks.…”

“…To minimize the effects of thermal history, the samples were cycled at a rate 10 C/min between ¡80 C and 240 C (for TPUs with the HS based on MDI and BDO) or between ¡80 C and 200 C (for TPUs with the HS based on HDI and BDO), and data from the second heating were used. According to literature, the highest temperature is above the melting point of HS based on MDI and BDO (19)(20)(21) and HS based on HDI and BDO (22)(23)(24)(25), allowing enough mobility for both the HS and SS.…”

Physics of engineered protein hydrogels

“…It is noteworthy that the molecular architecture of silk proteins resembles the design of synthetic polyurethane elastomers. [125][126][127] In both silks and polyurethanes, semicrystalline regions establish crosslinks and provide the modulus and toughness, whereas amorphous regions allow stress distribution and homogenization to provide elasticity. 128,129 The hydrophobic interactions and hydrogen bonding among Ala-rich and Ala-Gly-rich repeat sequences in silk drive the formation of b-sheets.…”