We have synthesized a novel benzoxazine monomer and polybenzoxazine thermosetting resin based on urushiol, a natural product. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) studies demonstrate that the thermally activated ring opening polymerization of the benzoxazine occurs at around 210 °C without addition of catalyst. Thermal gravimetric analysis (TGA) measurements show the temperatures corresponding to 5% and 10% weight loss are 325 °C and 357 °C, respectively, with a char yield of 22% at 600 °C. Dynamic mechanical analysis (DMA) studies indicate the urushiol-based polybenzoxazine exhibits excellent toughness with a storage modulus (G′) of 606 MPa at room temperature and an elongation at break of 17.4%.

A reprocessable and chemically degradable thermoset with high T_g was synthesized via the incorporation of dynamic Si–O–Ph bonds.

The difunctional urushiol-based benzoxazine (U-da) was synthesized by utilizing urushiol, 4,4′-diaminodiphenyl methane (DDM) and formaldehyde. The 3,3′-phenylmethanebis(3,4-dihydro-2H-1,3-benzoxazine) (P-da) was prepared by the similar procedure with DDM, phenol and formaldehyde. The U-da and P-da were cured into hybrid polybenzoxazine with different U-da fractions, where the alkyl chains in urushiol can improve the ductility of the polybenzoxazines. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) studies demonstrate that the thermally activated ring-opening polymerization can happen at a relatively low temperature (∼180 °C) without addition of catalyst. The hybrid polybenzoxazines were measured by thermal gravimetric analysis (TGA). It shows the temperatures corresponding to the 5% and 10% weight loss are slightly affected by the U-da content whereas the residual weight at 800 °C increases with P-da content. Dynamic mechanical analysis (DMA) studies indicate that the hybrid polybenzoxazine with U-da content of 50 wt% has a relatively high elongation (10%) and stress (101 MPa) at break. The properties of the hybrid polybenzoxazine can be tuned by the composition.

Low cytotoxicity and high gene transfection efficiency are critical issues in designing current non-viral gene delivery vectors. The purpose of the present work was to synthesize the novel biodegradable poly (lactic acid)-poly(ethylene glycol)-poly(L-lysine) (PLA-PEG-PLL) copolymer, and explore its applicability and feasibility as a non-viral vector for gene transport. PLA-PEG-PLL was obtained by the ring-opening polymerization of Lys(Z)-NCA onto amine-terminated NH₂-PEG-PLA, then acidolysis to remove benzyloxycarbonyl. The tri-block copolymer PLA-PEG-PLL combined the characters of cationic polymer PLL, PLA and PEG: the self-assembled nanoparticles (NPs) possessed a PEG loop structure to increase the stability, hydrophobic PLA segments as the core, and the primary ε-amine groups of lysine in PLL to electrostatically interact with negatively charged phosphate groups of DNA to deposit with the PLA core. The physicochemical properties (morphology, particle size and surface charge) and the biological properties (protection from nuclease degradation, plasma stability, in vitro cytotoxicity, and in vitro transfection ability in HeLa and HepG2 cells) of the gene-loaded PLA-PEG-PLL nanoparticles (PLA-PEG-PLL NPs) were evaluated, respectively. Agarose gel electrophoresis assay confirmed that the PLA-PEG-PLL NPs could condense DNA thoroughly and protect DNA from nuclease degradation. Initial experiments showed that PLA-PEG-PLL NPs/DNA complexes exhibited almost no toxicity and higher gene expression (up to 21.64% in HepG2 cells and 31.63% in HeLa cells) than PEI/DNA complexes (14.01% and 24.22%). These results revealed that the biodegradable tri-block copolymer PLA-PEG-PLL might be a very attractive candidate as a non-viral vector and might alleviate the drawbacks of the conventional cationic vectors/DNA complexes for gene delivery in vivo.