The structural development of a segmented poly(urethane−urea) (PUU) elastomer containing a low concentration of hard segment during deformation was studied by simultaneous mechanical and optical measurements (rheooptical techniques). Specifically, in-situ wide-angle X-ray diffraction and small-angle X-ray scattering using synchrotron radiation and time-resolved Fourier transform infrared spectroscopy were applied to investigate the segmental orientation of PUU chains during cyclic elongation and recovery. Formation of two different domain microstructures is characterized with changes in strain. These microstructures consist of lamellar hard domains and highly stressed nanofibrils consisting of alternating hard and crystalline soft domains. By comparing the X-ray scattering and vibrational spectroscopic data, a morphological model of hard- and soft-segment microphase separation, orientation, and strain-induced crystallization in the soft segments was obtained.

In-Situ Studies of Structure Development during Deformation of a Segmented Poly(urethane−urea) Elastomer

Zero-order release of lysozyme from poly(ethylene glycol)/poly(butylene terephthalate) matrices

This paper reports the gas-permeation properties of poly(ethylene oxide) (PEO) poly(butylene terephthalate) (PBT) segmented multiblock copolymers. These block copolymers allow a precise structural modification by the amount of PBT and the PEO segment length, enabling a systematic study of the relationship between polymer composition and morphology and gas-transport properties. The CO2 and N2 permeability strongly varies with the amount of PEO and the PEO segment length. The permeabilities are compared to predictions of the Maxwell model, which considers the PBT phase as impermeable. The difference between the experimental values and the Maxwell model are interpreted on the basis of chain flexibility of the PEO phase. The chain flexibility decreases with increasing amounts of PBT due to a less pronounced phase separation between the PEO and PBT phase. This is reflected in an increasing glass-transition temperature of the amorphous PEO phase. The increase of the permeability with an increasing PEO block length, at the same ratio PEO-PBT, can therefore be related to a larger chain flexibility for longer PEO segments. The permeability also depends on the degree of crystallinity and the melting temperature of the PEO phase, which increases with the amount and the PEO segment length. PEO-PBT block copolymers exhibit a high CO2/N2selectivity ( 60 at T = 35 C) due to the high solubility of CO2 in the PEO phase. However, this selectivity is structure-dependent and is higher for block copolymers with larger amounts of PBT. The CO2/He selectivity shows a different structure dependency since the permeation of CO2 occurs primarily through the PEO phase and the He permeation occurs through both the PEO and mixed PEO-PBT interphase. Therefore, block copolymers with a better phase separation between the PEO phase and the PBT phase show a higher CO2/He selectivity.

Gas-permeation properties of poly(ethylene oxide) poly(butylene terephthalate block copolymers

This article reviews the degradability of chemically synthesized bioelastomers, mainly designed for soft tissue repair. These bioelastomers involve biodegradable polyurethanes, polyphosphazenes, linear and crosslinked poly(ether/ester)s, poly(e-caprolactone) copolymers, poly(1,3-trimethylene carbonate) and their copolymers, poly(polyol sebacate)s, poly(diol-citrates) and poly(ester amide)s. The in vitro and in vivo degradation mechanisms and impact factors influencing degradation behaviors are discussed. In addition, the molecular designs, synthesis methods, structure properties, mechanical properties, biocompatibility and potential applications of these bioelastomers were also presented.

https://www.mdpi.com/1422-0067/10/10/4223/pdf

Recent Advances in Synthetic Bioelastomers

A controlled release system for proteins based on poly(ether ester) block-copolymers: polymer network characterization.

The structure and phase transitions of block copolymers of PBT and PEO having different composition were investigated by DSC, SAXS, and WAXS. Two different glass transitions and two melting points were observed. The increase of the integral SAXS intensity with temperature was much smaller than in the case of homopolymers, which is explained by a broad melting range. The long period strongly increases with temperature, which is attributed to growth of domains.

P. Boeseke

Papers

Structure of segmented poly (ether ester)s as revealed by synchrotron radiation