Abstract:Cellulose gel (CG)/poly(ε-caprolactone) (PCL) composites showed extraordinary mechanical properties compared with pure PCL. The tensile maintained quite good even at temperature 40℃ higher than the melting point of PCL. CG/PCL composite was prepared by in-situ ring-opening polymerization. The structure of CG/PCL composites was characterized by XRD, DCS and solid-state NMR. The mass ratio of CG to PCL of composites was measured by quantitative solid-state ¹³C-CP/MAS NMR. The mass ratio of the grafted chains to free chains of PCL in the composites was also obtained. By solid-state ¹H-MAS NMR, the average molecular weight of PCL in the composites was measured. To understand the reinforcement mechanism of the CG/PCL composite, molecular motion of the composites at different temperatures was also studied. Solid-state ¹H-MAS NMR spectra showed that the full width at half maximum of the composites was significantly wilder than that of pure PCL, indicating that there was a strong dipole-dipole interaction between CG and PCL. The relationship between spin-spin relaxation time (T₂) and temperature showed quite different trends for pure PCL and PCL in the composites. T₂ of pure PCL showed a sudden increase when temperature increased to near melting point, while for PCL in the composite, the change was not so sharp. Results showed that the molecular motion of PCL chain was restricted by CG, which made the substantial increase of the thermo stability and high-temperature strength. From the other side, the molecular chains of CG were also influenced by PCL, leading to slight increase of its molecular motion, which made the composite much more flexible than pure CG.