Synthesis and Properties of Trehalose-Based Flexible Polymers Prepared from Difurfurylidene Trehalose and Maleimide- Terminated Oligo(dimethylsiloxane) by Diels-Alder Reactions

Abstract: Difurfurylidene trehalose (DFTreh) was synthesized from trehalose and furfural by an acetalization reaction. Maleimide-terminated dimethylsiloxane oligomers (DMS-BMI) were synthesized from amine-terminated dimethylsiloxane oligomers by condensation with maleic anhydride. Three types of DMS-BMI with different length were prepared. Trehalose-based polymers were synthesized by Diels-Alder reaction of DFTreh and DMS-BMI. The reaction proceeded at 40~70 °C to produce a polymer with a maximum weight average molecular weight of ~19,000. The thermal degradation temperature increased with the increase of the length of the oligo(dimethylsiloxane) units. The differential scanning calorimetry (DSC) measurements revealed the glass transition temperature (T_g) of the polymer at -130~-120 °C, and no distinct T_g not observed above room temperature in the DSC measurement. The polymer products are not liquid at room temperature, and solid films can be obtained by casting from solution, implying a phase-separated structure made up of soft and hard segments. The phase-separated structure was confirmed by transmission electron microscope (TEM) study. The DSC curve of the polymer showed a broad endothermic peak at 110~160 °C, suggesting that a retro-Diels-Alder reaction occurred. When a N,N-dimethylformamide solution of the polymer was kept at 100 °C and the resulting solution was analyzed by gel permeation chromatography (GPC), the molecular weight decreased and monomers appeared.