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In this paper, we discuss the functionalization of halloysite aluminosilicate clays (HNT) with anionic surfactant – sodium dodecanoate (NaL) and their use in new polymeric nanocomposites preparation via solvent casting. The selected polymer matrix were segmented; copoly(ester-ether)s – poly(butylene succinate-co-ethylene glycol) (PBS-EG) were synthesized for the first time with the use of enzymatic catalyst fromCandida antarcticalipase B. The influence of variable concentration of NaL, temperature, and time on functionalization and finally on the chemical structure (IR) and colloidal stability (zeta potential) of functionalized HNT (f-HNT) was examined. Nanocomposites were prepared via solvent casting process, where 1 wt% of HNTs and 1 wt% of f-HNT clays were added to the (e)PBS-EG solution in chloroform. The chemical structure, topography, and hydrophilic/hydrophobic properties of prepared nanocomposites were determined by nuclear magnetic resonance (1H NMR), infrared spectroscopy (IR), scanning electron microscopy, and water contact angle. It was observed that higher concentration of NaL, longer modification time, and higher temperature lead to even distribution of f-HNT into (e)PBS-EG matrix. Halloysite clays in general improved the hydrophilicity of (e)PBS-EG and f-HNT was found to act as nucleating agent during polymer crystallization. [ABSTRACT FROM PUBLISHER]

To systematically investigate the synthesis of poly(butylene succinate)-co-(dilinoleic succinate) (PBS-DLS) copolymers and to enrich the library of polyesters synthesized via a sustainable route, we conducted a two-step polycondensation using fully biobased monomers such as diethyl succinate (DS), 1,4-butanediol (1,4-BD) and dilinoleic diol (DLD) in diphenyl ether, using Candida Antarctica lipase B (CAL-B) as biocatalyst. A series of PBS-DLS copolyesters with a 90-10, 70-30 and 50-50 wt% of hard (PBS) to soft (DLS) segments ratio were compared to their counterparts, which were synthesized using heterogenous titanium dioxide/silicon dioxide (TiO2/SiO2) catalyst. Chemical structure and molecular characteristics of resulting copolymers were assessed using nuclear magnetic spectroscopy (1H- and 13C-NMR) and gel permeation chromatography (GPC), whereas thermal and thermomechanical properties as well as crystallization behavior were investigated by differential scanning microscopy (DSC), dynamic mechanical thermal analysis (DMTA), digital holographic microscopy (DHM) and X-ray diffraction (XRD). The obtained results showed that, depending on the type of catalyst, we can control parameters related to blockiness and crystallinity of copolymers. Materials synthesized using CAL-B catalysts possess more blocky segmental distribution and higher crystallinity in contrast to materials synthesized using heterogenous catalysts, as revealed by DSC, XRD and DHM measurements. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present the results of comparative dynamic stress relaxation studies performed with poly(styrene-b-isobutylene-b-styrene) (SIBS), polyurethane (PU) and polyester (PED) biomaterials in air and simulated body fluid (SBF) at 24°C and 37°C. SIBS showed the highest value of relieved stress under constant strain (24.1% after 100,000 cycles in air) with PED and PU having similar relative change (12.2% and 10.5%). In spite of its softness (Shore A 56 vs. 80), the dynamic modulus (E dyn) and stiffness of SIBS were in between PED and PU. The behavior of the materials was correlated to their structure: SIBS is an amorphous block copolymer with a long elastomer midblock, while PU and PED are semicrystalline segmented copolymers with much shorter soft blocks, and hydrogen bonding. SIBS and PED were relatively insensitive to SBF and temperature changes, while PU experienced the largest changes in physical properties in vitro (simulated body fluid, 37°C). [Copyright &y& Elsevier]

The goal of this research was the synthesis and thermal characterization of poly(ester-siloxane) multiblock copolymers. Poly(butylene terephthalate) (PBT) was the polyester block. α, ω-Diamino-terminated poly(dimethylsiloxane) (PDMS) was reacted with an excess of dimerized fatty acid to form a dicarboxy-terminated oligomer containing stable amide links. Multiblock copolymers were obtained in a three-stage process: oligomer preparation, transesterification, and polycondensation from the melt. A magnesium-titanate catalyst was used for transesterification and polymer formation (polycondensation). The synthesized oligomer was considered to be the soft segment and its content ranged from 20 to 45% by weight. Multiblock copolymers showed microphase separation as determined by differential scanning calorimetry (DSC). Their morphology was studied by optical microscopy (OM) and showed spherulitic ordering. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present the first results on the effect of specimen size and branching on the fatigue properties of polyisobutylene-based thermoplastic elastomers measured by the hysteresis method. It was verified that smaller specimens were inherently stronger as expected; at the same loading rate microdumbbells induced higher strain rates so they can be considered as the “worst case” scenario. Microdumbbells, which can be implanted into small animals for in vivo studies, were used for dynamic fatigue testing of linear poly(styrene-b-isobutylene-b-styrene) triblock copolymers (L_SIBS) in comparison with long-chain branched (tree-like or dendritic) versions (D_SIBS). In dynamic stress relaxation studies, D_SIBS performed better than L_SIBS. Simulated physiological conditions had negligible effect on the dynamic properties. [Copyright &y& Elsevier]