Poly (L-lactic acid) (PLLA) suggests attractive biomedical applications in drug releasing system, surgical suture, bone fixing and tissue repairing due to its degradable and biocompatible benefits. However, currently developed catalysts with high toxicity and currently reported PLLA with uncontrollable crystallinity are detrimental for the environmental protection and human health. Herein, we proposed a novel and effective approach to synthesizing PLLA using environmentally-friendly bio-based phenol-substituted triisobutylaluminum as the catalyst. The effects of the chemical structures of various bio-based phenols on the polymerization activity and stereoregularity of PLLA were explored in detail. The increased steric hindrance of bio-based phenols was beneficial for the polymerization activity of PLLA. The resultant PLLA exhibited an ultrahigh monomer conversion efficiency up to 98.32% among the highest value of reported PLLA. Moreover, the PLLA also demonstrated quick polymerization rate (< 5 h) and low polymerization temperature (< 100 °C), with controllable polymer crystallinity (36 ~ 46%) and number average molecular weight (8400 ~ 16,000 g mol −1 ). Consequently, the strategy and results collectively represent a significant advance toward the preparation of high-performance degradable and biocompatible PLLA.
Phenolic resins were employed to prepare electrospun porous carbon nanofibers with a high specific surface area as free-standing electrodes for high-performance supercapacitors. However, the sustainable development of conventional phenolic resin has been challenged by petroleum-based phenol and formaldehyde. Lignin with abundant phenolic hydroxyl groups is the main non-petroleum resource that can provide renewable aromatic compounds. Hence, lignin, phenol, and furfural were used to synthesize bio-based phenolic resins, and the activated carbon nanofibers were obtained by electrospinning and one-step carbonization activation. Fourier transform infrared and differential scanning calorimetry were used to characterize the structural and thermal properties. The results reveal that the apparent activation energy of the curing reaction is 89.21 kJ·mol −1 and the reaction order is 0.78. The activated carbon nanofibers show a uniform diameter, specific surface area up to 1100 m 2 ·g −1 , and total pore volume of 0.62 cm 3 ·g −1 . The electrode demonstrates a specific capacitance of 238 F·g −1 (0.1 A·g −1 ) and good rate capability. The symmetric supercapacitor yields a high energy density of 26.39 W·h·kg −1 at 100 W·kg −1 and an excellent capacitance retention of 98% after 10000 cycles. These results confirm that the activated carbon nanofiber from bio-based phenolic resins can be applied as electrode material for high-performance supercapacitors.
Changhao Wu,Jixiao Wang,Fengrui Yang,Zhi Wang,Zhiye Sun
The utilization and conversion of renewable biomass is a promising strategy to attain sustainable society. Herein, full bio-based phenalkamine (FBA) was prepared using three bio-based raw materials, which were cardanol, furfural and 1,5-pentanediamine, by one-pot process based on Mannich reaction without catalyst and solvent. Then, FBA was used to cure epoxy under the condition of solvent-free, which can eliminate the negative effect of volatile organic solvents (VOCs). Attributed to the long chain, large steric hindrance and strong hydrophobicity of FBA, solvent-free FBA/epoxy coating had appropriate curing speed, non-defects morphologies, high flexibility (impact resistance height: 100 cm, bending resistant shaft diameter: 2 mm), low water absorption (0.65 wt%), and long-term protective performance (|Z| 0.01Hz = 1.23 × 10 9 Ω·cm 2 after 100 d immersion under harsh environment). Compared with partial bio-based phenalkamine (MD1041)/epoxy coating and petroleum-based phenalkamine (T31)/epoxy coating, FBA/epoxy coating had satisfactory underwater-cured protective properties (|Z| 0.01Hz >10 6 Ω·cm 2 after directly cured and immersed for 100 d in 5 wt% NaCl solution) based on the strong hydrophobicity and dense crosslink networks. Notably, FBA/epoxy coating had improved performance compared with purified FBA (PFBA)/epoxy coating, which was related to the high crosslink density coming from the residual 1,5-pentanediamine. This work provided some enlightenment to prepare solvent-free coating using full bio-based materials.
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