Crystallization hard segment

Zhu, Y, Hu, J. L., Yeung, Y. (2009b), Effect of soft-segment crystallization, hard segment physical cross-link on shape memory function in antibacterial segmented PU ionomers, Acta Biomaterials, 5, 3346-57. 

Gogolewski et al. " combined Pluronic F-68(poly(ethylene-propylene-ethylene oxide) with PCL within the same soft segment. BD or 2-amino-l-butanol was used as the chain extender and HDI as the hard segment. They observed that all the materials calcified and calcification increased with material hydrophilicity. The stmcture and composition of the calcium crystals formed on the materials depended on the PU chemistry. 

Today, new copolymers are making use of the hard-soft block strategy where the hard segment is a block portion as PE that readily crystallizes forming a physical cross-link. The soft segment consists of blocks formed from alpha-olefins, such as 1-butene, 1-hexene, and 1-octane, where the substituted alkane-arm discourages crystallization. 

Although short-segment sequences are expected to be the most compatible, the 1/2/1 random copolymer with an average hard-block-sequence length of only two units does exhibit a phase-separated morphology—as reflected for the as-reacted sample in hard-segment crystal-... 

The possibility also exists that the hard-segment domains are really crystalline, but the crystals are so small that they are not detected by WAXD. In this regard, small angle x-ray diffraction (SAXD) does detect the domains, so we know that they exist, that they have some order,... 

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