Two types of novel reactive linear liquid crystal polymers (LLCPs) with different azotolene concentrations have been synthesized and processed into films and fibers by solution and melting processing methods. Then, the LLCPs in the obtained monodomain fiber and polydomain film were easily cross-linked with difunctional primary amines. The resulted cross-linked liquid crystal polymers (CLCPs) underwent reversible photoinduced bending and unbending behaviors in response to 445 and 530 nm visible light at room temperature, respectively. The post-cross-linking method provides a facile way to prepare the CLCP films and fibers with different shapes from LLCPs, which can be processed by traditional melting and solution methods.Keywords: azotolene; good processability; linear polymer; liquid crystal; photoinduced deformation;

Poly(l-lactide)/poly(ɛ-caprolactone) diblock, triblock and four-armed copolymers with the same monomer feed ratio (50/50) were synthesised by two step ring opening polymerisation of successively added ɛ-caprolactone and l-lactide, using isopropanol, ethylene glycol, or pentaerythritol as initiator and zinc lactate as co-initiator. The resulting copolymers were characterised by 1H NMR, DSC, SEC, and FT-IR, which confirmed the blocky characteristic of the copolymers. Solution cast films were allowed to degrade at 37 °C in the presence of proteinase K, and the degradation was monitored by gravimetry, DSC, SEC, 1H NMR and ESEM. The effects of chain structure, block length and crystallinity on the degradation are discussed. The four-armed block copolymer degrades the most rapidly, while the diblock copolymer exhibited the slowest degradation rate. The difference was related to the crystallinity depending on both the molecular structure and block length. Little compositional or molar mass changes were obtained during degradation, which strongly supports a surface erosion mechanism, in agreement with ESEM observations.

Copolymers of polylactide (PLA) and poly(ethylene glycol) (PEG) were synthesized by ring-opening polymerization of l- or d-lactide in the presence of mono- or dihydroxyl PEG using nontoxic zinc lactate as catalyst. The resulting diblock and triblock copolymers were characterized by various analytical techniques such as SEC, 1H NMR, XRD, and DSC. Bioresorbable micelles were prepared from aqueous solutions of the various copolymers without using any organic solvent. The mixed micellar solutions containing both L-PLA/PEG and D-PLA/PEG copolymers appeared more stable than the separate solutions according to critical micellar concentration (CMC) results, which could be assigned to stronger interactions between L-PLA and D-PLA blocks. The properties of the polymeric micelles strongly depend on the chain structure and composition of the copolymers. CMC values in the presence of salt and at 37 °C suggested that the micelles could exhibit good stability in vivo. Thermodynamic parameters calculated from the dependence of CMC on temperature indicate that the micellization process is spontaneous and driven by entropy gain. Dynamic light scattering (DLS) measurements showed one or two populations of micelles for dilute and concentrated solutions, the micelle size decreasing upon dilution. TEM confirmed the presence of micelles, but the size estimated from TEM was smaller than that from DLS due to the dehydration and shrinkage during drying.Triblock copolymers of polylactide (PLA) and poly(ethylene glycol) (PEG) were synthesized by ring-opening polymerization of l- or d-lactide in the presence of dihydroxyl PEG using nontoxic zinc lactate as catalyst. Diblock copolymers were obtained similarly by using mono-hydroxyl PEG.

Copolymers of ɛ-caprolactone and l-lactide with different molar ratios were prepared via sequential ring opening polymerization (ROP) of both monomers. The resulting PCL–PLLA–PCL triblock copolymers were characterized by using NMR, SEC, DSC and XRD. One melting peak corresponding to the PCL block was detected, but the presence of PLLA decreased the crystallinity of PCL. Enzyme-catalyzed biodegradation of solution cast films was investigated at 37 °C in the presence of Pseudomonas lipase. It was observed that the PLLA component retarded the degradation of the block copolymer as compared to the PCL homopolymer. Therefore, the enzymatic degradation rate can be adjusted by varying the composition of the copolymers. 1H NMR and SEC data showed no significant chemical composition or molecular weight changes during degradation, indicating that the degradation proceeded according to a surface erosion mechanism. ESEM confirmed surface erosion with appearance of a rugged morphology.