Biodegradable Thermoplastic Elastomers Incorporating POSS: Synthesis, Microstructure, and Mechanical Properties

Dynamic Ablative Networks: Shapeable Heat-Shielding Materials

Thermoset materials sacrifice recyclability and reshapeability for increased chemical and mechanical robustness because of an immobilized, cross-linked polymeric matrix. The robust material properties of thermosets make them well-suited for applications such as heat-shielding materials (HSMs) or ablatives where excellent thermal stability, good mechanical strength, and high charring ability are paramount. Many of these material properties are characteristic of covalent adaptable networks (CANs), where the static connectivity of thermosets has been replaced with dynamic cross-links. This dynamic connectivity allows network mobility while retaining cross-link connectivity to permit damage repair and reshaping that are traditionally inaccessible for thermoset materials. Herein, we report the synthesis of hybrid inorganic-organic enaminone vitrimers that contain an exceptionally high weight percent of polyhedral oligomeric silsesquioxane (POSS)-derivatives. Polycondensation of β-ketoester-containing POSS with various diamine cross-linkers led to materials with facile tunability, shapeability, predictable glass transition temperatures, good thermal stability, and high residual char mass following thermal degradation. Furthermore, the char materials show notable retention of their preordained shape following decomposition, suggesting their future utility in the design of HSMs with complex detailing.

Fabrication of PLCL Block Polymer with Tunable Structure and Properties for Biomedical Application

Biodegradable materials are pivotal in the biomedical field, where how to precisely control their structure and performance is critical for their translational application. In this study, poly(L-lactide-b-ε-caprolactone) block copolymers (bPLCL) with well-defined segment structure are obtained by a first synthesis of poly(ε-caprolactone) soft block, followed by ring opening polymerization of lactide to form poly(L-lactide acid)  hard block. The pre-polymerization allows for fabrication of bPLCL with the definite compositions of soft/hard segment while preserving the individual segment of their special soft or hard segment. These priorities make the bPLCL afford biodegradable polymer with better mechanical and biodegradable controllability than the random poly(L-lactide-co-ε-caprolactone) (rPLCL) synthesized via traditional one-pot polymerization. 10 mol% ε-caprolactone introduction can result in a formation of an elastic polymer with elongation at break of 286.15% ± 55.23%. Also, bPLCL preserves the unique crystalline structure of the soft and hard segments to present a more sustainable biodegradability than the rPLCL. The combinative merits make the pre-polymerization technique a promising strategy for a scalable production of PLCL materials for potential biomedical application.

Recent Advances in Polyurethane/POSS Hybrids for Biomedical Applications

Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties required in modern biomedical applications. When incorporated, chemically or physically, into polyurethane matrices, they substantially change polymer properties, including mechanical properties, surface characteristics, and bioactivity. Hence, this review is dedicated to POSS-PU composites that have recently been developed for applications in the biomedical field. First, different modes of POSS incorporation into PU structure have been presented, then recent developments of PU/POSS hybrids as bio-active composites for scaffolds, cardiovascular stents, valves, and membranes, as well as in bio-imaging and cancer treatment, have been described. Finally, characterization and methods of modification routes of polyurethane-based materials with silsesquioxanes were presented.

Sustainable Shape-Memory Polyurethane from Abietic Acid: Superior Mechanical Properties and Shape Recovery with Tunable Transition Temperatures

A new chemical architecture from abietic acid, consisting of a cycloaliphatic unsaturated terminal diisocyanate (AADI) structure, is synthesized and fully characterized. The AADI is then used to construct an amorphous and biocompatible shape-memory polyurethane (SMPU) network system with adjustable cross-linking densities over a wide range. The SMPU network exhibits good shape-memory properties with a shape fixing rate of greater than 98 % and a shape recovery rate of 95 %. In vitro hydrolytic biodegradation weight loss ratio of SMPUs reaches 71 % within eight weeks. The physical properties of these SMPUs are comparable to those reported for SMPUs obtained from commercially available petroleum-derived diisocyanates. This is the first time that multiple SMPU networks based on abietic acid have been reported. These environmentally-friendly SMPUs display a wide range of physicomechanical properties with promising hydrolytic degradability, showing good potential for practical application.

Stretchable Conductive Hybrid Films Consisting of Cubic Silsesquioxane-capped Polyurethane and Poly(3-hexylthiophene)

We fabricated stretchable and electric conductive hybrids consisting of polyhedral oligomeric silsesquioxane (POSS)-capped polyurethane (PUPOSS) and doped poly(3-hexylthiophene) (P3HT). In order to realize robust films coexisting polar conductive components in hydrophobic elastic matrices, we employed POSS introduced into the terminals of the polyurethane chains as a compatibilizer. Through the simple mixing and drop-casting with the chloroform solutions containing doped P3HT and polyurethane polymers, homogeneous hybrid films were obtained. From the conductivity and mechanical measurements, it was indicated that hybrid materials consisting of PUPOSS and doped P3HT showed high conductivity and stretchability even with a small content of doped P3HT. From the mechanical studies, it was proposed that POSS promoted aggregation of doped P3HT in the films, and ordered structures should be involved in the aggregates. Efficient carrier transfer could occur through the POSS-inducible ordered structures in the aggregates.

Synthesis and Porous SiO2 Nanofilm Formation of the Silsesquioxane-Containing Amphiphilic Block Copolymer

We describe the synthesis, Langmuir-Blodgett (LB) film formation, and photo-oxidation of an organic-inorganic hybrid block copolymer consisting of N-dodecyl acrylamide (DDA) and silsesquioxane (SQ) comonomers [p(DDA/SQ26)- b-pDDA]. The copolymer was synthesized by reversible addition fragmentation chain transfer polymerization of DDA and SQ. Higher monolayer stability at the air-water interface was confirmed for p(DDA/SQ26)- b-pDDA. The p(DDA/SQ26)- b-pDDA monolayer was deposited onto solid substrates with a monolayer thickness of 2.3 nm. The photo-oxidized SiO₂ nanofilm revealed its porous structure, which reflects phase-separated structures of p(DDA/SQ26)- b-pDDA, as confirmed using atomic force microscopy, quartz crystal microbalance, and cyclic voltammetry measurements. These results demonstrate that this preparation method using photo-oxidation of the organic-inorganic hybrid block copolymer LB film is promising for manipulating pore formations of inorganic oxide nanofilms.

An insight into the amphiphobicity and thermal degradation behavior of PDMS-based block copolymers bearing POSS and fluorinated units

Methacryloxypropyl-polyhedral oligomeric silsesquioxane (MAPOSS) and dodecafluoroheptyl methacrylate (DFHM) are proposed to separately block-copolymerize with polydimethylsiloxane (PDMS)-based acrylate block copolymer (PDMS-b-PMMA). The syntheses of PDMS-b-PMMA-b-PMAPOSS and PDMS-b-PMMA-b-PDFHM were executed in this manner to examine the effect of PMAPOSS and PDFHM on surface amphiphobic behavior and thermal degradation behavior. PMAPOSS and PDFHM were found to both contribute towards the improvement of static hydrophobicity. However, the PMAPOSS was found to disable the dynamic hexadecane-dewetting properties because of its restriction on molecular wriggling motion and its induced high roughness. In contrast, PDFHM was found to improve the dynamic dewetting properties for oil-based ink. With regard to the thermal stability, the incorporation of either PMAPOSS or PDFHM into PDMS-b-PMMA with PDMS (Mn ∼1000 or 5000 Da) favors the increase in the original thermal-decomposition temperature. However, the presence of PMAPOSS initiates a higher degradation rate and fails to improve the thermal stability in the case of long PDMS (Mn ∼10 000 Da) due to the heterogeneous dispersion of POSS in the matrix.

Synthesis, characterization and potential applications of 5-hydroxymethylfurfural derivative based poly(β-thioether esters) synthesized via thiol-Michael addition polymerization

Dimethylphenylphosphine was used to efficiently initiate the thiol-Michael addition polymerization to yield 5-hydroxymethylfurfural (HMF) derivative based poly(β-thioether esters) with relatively high molecular weights (over 10 000 g mol⁻¹) under mild conditions.