No abstract

Castor oil (CO)-derived polyurethanes (PUs), denoted CPUs, are drastically limited because they cannot be reprocessed, reshaped, or recycled and because they show low strength, poor toughness, and insufficient functionality due to their permanently cross-linked structure with a high cross-link density and a soft backbone. Herein, we developed novel reversible piperazine−urea bonds (PaUBs) from inexpensive piperazines and isocyanates and incorporated the PaUBs into CPUs to fabricate sustainable and reprocessable poly(urethane urea) covalent adaptable networks (CANs). We synthesized the CANs from CO, N-(2-hydroxyethyl) piperazine (HEP), and 4-methylenedicyclohexyl diisocyanate (HMDI) via a catalyst-and solvent-free approach. The CANs showed variable tensile behavior over a wide range from a soft elastomer to tough and hard plastics. They also exhibited excellent malleability, stable reprocessability, and multiple recyclability, in which their original properties were recovered after several thermal recycling or remolding cycles. The CANs possessed excellent shape memory performance and reconfigurability, allowing them to be reprocessed into various complex shapes without using a mold. The advanced sustainable CANs based on dynamic PaUBs have great potential application as alternatives to traditional fossil-derived elastomers and plastics.

No abstract

No abstract

Graphene oxide (GO) and ball‐milled maleamic acid–isobutyl polyoctahedral silsesquioxanes (MAIPSs) were incorporated simultaneously into chitosan (CS) via solution blending to evaluate their combined effects on the structures and properties of composite films. GO and MAIPS aggregates were homogeneously dispersed in CS and affected the crystallinities of the composite films. The binary addition of GO and MAIPS resulted in synergistic enhancements of the tensile strength and elongation at break of the composite films. Composite films containing 3% w/w MAIPS and 0.25% w/w GO (CS–GO–MAIPS‐3) exhibited the highest strength and modulus, which were 48 and 42.2% higher, respectively, than the values of the CS film. The water‐vapor‐sorption isotherms revealed that monolayer sorption sites decreased with the addition of GO or/and MAIPS, but the dissolution process was not significantly influenced. The water‐vapor permeability reached its lowest value for the CS–GO–MAIPS‐3 film because of hindered diffusion with the presence of impermeable nanoparticles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47748.