Controlling the switching temperature of biodegradable shape memory polymers composed of stereocomplex polylactide / poly(,-lactide-co-ε-caprolactone) blends

A comparative study of titanium complexes bearing 2-(arylideneamino)phenolates and 2-((arylimino)methyl)phenolates as catalysts for ring-opening polymerization of ε-caprolactone and L-lactide

Titanium complexes bearing 2-(arylideneamino)phenolates and 2-((arylimino)methyl)phenolates were synthesized, and their catalytic activities in the polymerization of ε-caprolactone and L-lactide were studied. Among five-membered ring Ti complexes bearing 2-(arylideneamino)phenolates, FCl-Ti exhibited the highest level of catalytic activity ([CL] : [FCl-Ti] = 100 : 1, where [CL] = 2 M, and conv. = 86% at 60 °C after 9 h). For six-membered ring Ti complexes bearing 2-((arylimino)methyl)phenolates, SCl-Ti exhibited the highest level of catalytic activity ([CL] : [SCl-Ti] = 100 : 1, where [CL] = 2 M, and conv. = 88% at 60 °C after 118 h). The five-membered ring Ti complexes bearing 2-(arylideneamino)phenolates exhibited a higher level of catalytic activity (6.1-12.8 fold for the polymerization of ε-caprolactone and 6.2-23.0 fold for the polymerization of L-lactide) than the six-membered ring Ti complexes bearing 2-((arylimino)methyl)phenolates. The density functional theory (DFT) results revealed that the free energy of the first transition state FH-Ti-TS1 is 36.49 kcal mol-1 which is lower than that of SH-Ti-TS1 (46.58 kcal mol-1), which was ascribed to the fact that the Ti-Nim bond (2.742 Å) of FH-Ti-TS1 is longer than that of SH-Ti-TS1 (2.229 Å) and reduces the repulsion between ligands.

Multifunctionality of Iodinated Halogen-Bonded Polymer: Biodegradability, Radiopacity, Elasticity, Ductility, and Self-Healing Ability

A polymer with high contents of ester bonds and iodine atoms was synthesized, exhibiting sufficient biodegradability and radioactivity for biomedical applications. The iodine moieties of the synthesized polyester can generate halogen bonding between molecules, which may develop additional functional properties through the bonding. In this study, poly(glycerol adipate) (PGA) was selected and synthesized as a polyester, which was then adequately conjugated with three different types of iodine compounds via the hydroxy groups of PGA. It was found that the iodine compounds could effectively work as donors of halogen bonding. The thermal analysis by differential scanning calorimetry (DSC) revealed that the glass transition temperature increased with the increase in the strength of interactions caused by π-π stacking and halogen bonding, eventually reaching 49.6 °C for PGA with triiodobenzoic groups. An elastomeric PGA with monoiodobenzoic groups was also obtained, exhibiting a high self-healing ability at room temperature because of the reconstruction of halogen bonding. Such multifaceted performance of the synthesized polyester with controllable thermal/mechanical properties was realized by halogen bonding, leading to a promising biomaterial with multifunctionality.

Development of poly(butylene adipate-co-butylene succinate-co-ethylene adipate-co-ethylene succinate) (PBEAS) net twine as biodegradable fishing gear

Nylon fishing nets have excellent strength and durability, but when lost at sea, their insufficient decomposition destroys habitats and spawning grounds, and pollutes the marine environment. This led to the development of poly(butylene succinate) (PBS) resin for biodegradable fishing gear based on aliphatic fibers. Prompted by the low stiffness and elastic recovery of PBS, we introduced two additional components into the molecular structure of PBS: adipic acid and ethylene glycol. These two new components were combined with succinic acid and 1,4-butanediol, the existing components of PBS, to synthesize poly(butylene adipate-co-butylene succinate-co-ethylene adipate-co-ethylene succinate) (PBEAS) resin via esterification and polycondensation reactions of a quaternary aliphatic copolyester. Although the molecular weight and molecular weight distribution of PBEAS are similar to those of PBS, it has excellent tensile strength, stiffness, elastic recovery, and biodegradability, with a low melting point for good production efficiency. These improvements are expected to allow PBEAS resin to be applied to gill nets for fish that require high stiffness, thereby expanding the use of biodegradable fishing gear.

Effects of Chemical Composition on the Shape Memory Property of Poly(dl-lactide-co-trimethylene carbonate) as Self-Morphing Small-Diameter Vascular Scaffolds

Smart materials have great potential in many biomedical applications, in which biodegradable shape memory polymers (SMPs) can be used as surgical sutures, implants, and stents. Poly(dl-lactide-co-trimethylene carbonate) (PDLLTC) represents one of the promising SMPs and is widely used in biomedical applications. However, the relationship between its shape memory property and chemical structure has not been fully studied and needs further elaboration. In this work, PDLLTC copolymers in different compositions have been synthesized, and their shape memory properties have been investigated. It has been found that the shape memory property is related to the chemical composition and polymeric chain segments. The copolymer with a DLLA/TMC ratio of 75:25 (PDLLTC7525) has been demonstrated with great shape fixation and recovery ratio at human body temperature. Furthermore, PDLLTC7525-based self-morphing small-diameter vascular scaffolds adhered with inner electrospun aligned gelatin/hyaluronic acid (Gel/HA) nanofibers have been constructed, as a merit of its shape memory property. The scaffolds have been demonstrated to facilitate the proliferation and adhesion of endothelial cells on the inner layer. Therefore, PDLLTC with tailorable shape memory properties represents a promising candidate for the development of SMPs, as well as for small-diameter vascular scaffolds construction.

A drug-loaded amphiphilic polymer/poly(l-lactide) shape-memory system

Biodegradable shape-memory polymers (SMPs) which are functional materials with applicability for medicine devices are designed to acquire their therapeutically relevant shape and drug release after implantation. In the work, an amphiphilic polymer (PVAD) is synthesized by using polytetrahydrofuran (PTMG), vinyl acetate (VAc), acrylic acid (AA), tetramethyltetravinylcyclotetrasiloxane (D₄^vi) as raw materials. PVAD encapsulating hydrophilic drug as switching phase and poly(l-lactide) (PLLA) as fixing matrix construct an SM system with the characteristic of "reservoir-matrix" drug release. The shape recovery ratio (R_r) of medicated PVAD/PLLA reaches 99 % by heat-water stimulation. The effects of release temperature and SM on drug release are investigated. With the release temperature increasing, the medicated PVAD/PLLA accelerates drug release and shows burst release initially, while the drug release for the medicated PLLA changes slightly. The drug release rate goes up after 3 rounds of SM. The mechanism of SM system controlling drug release is put forward based on structural changes. The yield strength and elongation at break of medicated PVAD/PLLA are 29.8 MPa and 44.6 %, respectively. It opens up new perspectives for drug carrier matrices in Pharmaceutical Sciences.