Nonisocyanate polyurethane (NIPU) has been extensively studied because of its sustainability potential. However, the low reactivity of five-membered cyclocarbonates with amines and the side reactions at higher temperatures always sacrifice the performance of NIPUs. In this work, a bisphenol-S cyclic thiocarbonate and different amino-terminated dimer-acid polyamides (DAPAs) were used to prepare nonisocyanate polythiourethanes (SPTU-DAs). Wherein bisphenol-S acts as a hard segment due to a π−π package, plentiful hydrogen bonds introduced by DAPA units induce crystallization and nanophase separation. They both endow the NIPUs with high mechanical performance. Meanwhile, active cyclic thiocarbonate, instead of cyclic carbonate, ensures rapid synthesis under mild conditions without side reactions. The experimental results of DSC, WAXD, and DMA confirmed the existence of crystallization of SPTU-DAs. The as-prepared thermoplastic polythiourethane has a maximum strength of more than 10 MPa, which is stronger than those of the cross-linked nonisocyanate polythiourethanes reported. It is of key significance to obtain the high performance of nonisocyanate polythiourethanes.

Microcrystalline cellulose (MCC) is regarded as a potential filler in the fabrication of epoxy composites. However, MCC’s hydrophilic nature and strong hydrogen bonds caused by abundant surface hydroxyl groups greatly weaken its compatibility with the epoxy resin. In addition, it remains a challenge to efficiently and heterogeneously modify MCC surface hydroxyl groups. In this work, MCC was epoxidized heterogeneously with a phase-transfer catalyst. Results indicated that 4.48% (by mass) or 58.15% (by coverage) of the hydroxyl groups on MCC was modified. The dispersibility of epoxidized MCC (EP-MCC) in the epoxy resin was significantly improved. At the same time, EP-MCC showed the ability to interact with the epoxy network covalently, improving the interface interactions, indicating the simultaneous enhancement of the modulus and the toughness. As a result, this heterogenous epoxidation method showed high efficiency in reducing the surface hydroxyl content of MCC, endowing it with a bright future in industrial applications of epoxy composites.