Fully biobased poly(L-lactide)-b-polymyrcene-b-poly(L-lactide) triblock copolymers with PLLA as the hard block and polymyrcene as the soft block were synthesized by the ring opening polymerization of L-lactide in the presence of the dihydroxyl-terminated polymyrcene precursor and organocatalyst. The copolymer composition and molecular weight of these triblock copolymers were confirmed by NMR and GPC results. Two separated glass transition temperatures were detected by both DMA and DSC techniques, indicating an existence of micro-phase separation in these triblock copolymers, which is a typical characteristic of thermoplastic elastomers with the content of soft block increases. Tensile testing revealed that PLLA-b-PM-b-PLLA (200) having 20 wt% polymyrcene show distinct yielding while other samples fracture at low strain without yielding. POM results indicated that all these spherulites show the same characteristic “Maltese cross” patterns. With the increasing content of polymyrcene, the perfection of spherulites decreases, especially for PLLA-b-PM-b-PLLA (200). Considering the current energy and environmental problems, it is expected that these fully biobased thermoplastic elastomers will be of great significance in expanding the applications of PLLA and solving the ecological crisis around us.

This study demonstrates an efficient method for the synthesis of thermoreversible cross-linked ethylene/propylene rubbers (EPRs) via two steps; in the first step, a functional olefin monomer containing a furan group (FO) is designed and the ethylene/propylene/FO terpolymerization catalyzed by a traditional Ziegler–Natta catalyst is implemented; in the second step, a cross-linked network is constructed via Diels–Alder (DA) click reaction between the bismaleimide and pendant furan groups in the EPR chains. Via polymerization, the FO content in the copolymers was tailored in relatively wide range from 1.1 mol% to 9.7 mol%; this provided various cross-linking precursory groups for the DA reaction. Moreover, the cross-linking density could be adjusted via not only the amount of the inserted furan group but also the ratio of furan to bismaleimide. These solid thermoreversibile EP rubbers could perform their de-cross-linking above 110 °C and re-form the network below 85 °C in a heating–cooling cycle not only in the static measurement of FTIR, but also in the dynamic test of DMA. The mechanical properties of the resulting products with varied cross-linking densities were compared with that of the non-cross-linked polymer and proved to be of much higher modulus. This thermoreversible cross-linking behavior also provided a new strategy for local-repairing of any crack in rubber products.

Due to their distinct steric hindrance, 1,1-diphenylethylene (DPE) and its derivatives cannot homopolymerize via living anionic polymerization and thus are advantageous for investigating the sequence structure of the corresponding copolymers. The substitution of functional groups on the benzene rings of DPE derivatives can be used to adjust the reactivity ratios for the copolymerization of styrene and the DPE derivatives. Two types of DPE derivatives, DPE-SiH/OMe and DPE-SiH/NMe₂, were designed and prepared in this work. An electron withdrawing substituent and an electron donating substituent are simultaneously present at the para positions of the two phenyl rings of DPE. These derivatives were copolymerized with styrene under Schlenk conditions via living anionic polymerization. The statistical in-chain functionalized copolymers were prepared, and the corresponding average reactivity ratios were 1.42 for DPE-SiH/OMe and 1.79 for DPE-SiH/NMe₂. Additionally, a time sampling strategy under high vacuum conditions was used during the copolymerization of the two systems (styrene with DPE-SiH/OMe and styrene with DPE-SiH/NMe₂) with [M_S]₀/[M_D]₀ = 4. The propagation rate constants and statistical sequence structures were analyzed by ¹H NMR spectroscopy, SEC and MALDI-TOF MS, and the average sequential arrangements of the corresponding copolymers were determined. The critical conditions for preparing copolymers with alternating structures were determined and implemented, and the monomer unit ratios were both nearly 1 : 1.