Biobased polymers have long been recognized as alternatives to fossil-based counterparts. Although tremendous progress in this field has been witnessed in the last decades, performance-advantaged biobased polymers are still rarely reported. Herein, betulin and betulinic acid-derived high glass transition temperature (Tg) thermoplastics are prepared and preliminarily developed as functional materials. At first, norbornene derivatives (monomers M1 and M2) having betulinic units were obtained by means of esterification. Subsequently, homopolymers P1 and P2 in conjunction with statistical copolymers P3-P6 were synthesized via ring-opening metathesis polymerization (ROMP). In spite of their amorphism, these samples all possess Tgs exceeding 202.5 °C owing to the bulkiness and rigidity of their alicyclic pendent groups. Notably, an increase in Tg is observed as the molar fraction of the M1 unit becomes pronounced within the polymer composition. In particular, homopolymer P1 exhibits an exceptionally high Tg at 241.6 °C among alicyclic biobased polymers. Meanwhile, these specimens show good thermal stability, reprocessability, anticorrosiveness, hydrolysis resistance, and high tolerance to boiling water/nonsolvent given the hydrophobicity and structural rigidity of their frameworks. On the other hand, homogeneous mixing inorganic fillers (e.g., toner, magnetite, and terbium-containing particles) with these polymer matrices readily produce colored, magnetic, and phosphorescent hybrid materials. Furthermore, a postmodification strategy was employed to create fluorescent polymer P7 by anchoring pyrene units on the side chains of pristine polymer P1. This modified polymer can be potentially used in information encryption (optical anticounterfeiting).
Li et al. (Thu,) studied this question.