Synthesis And Characterization Of Biodegradable IPNs With Shape-memory Characteristics

Polymer materials has been applied widely and progressed in medical range in the recent 20 years. Among biomaterials, polymer material is most widespread in medical material for the nature of viscoelastic and strength adjustment, so that the mechanic performance is easy to match to the organ. Biodegradable shape-memory polymers are one of them that can be extensively investigated in the medical range has been attentioned recently. In this thesis, various IPNs were synthesis through photopolymerization and then thermal polymerization, the mechanical properties, degradability and shape-memory capabilities of these materials have been studied.Firstly, D, L-lactide was synthesized from D, L-lactic acid. The high purity of D,L-lactide was affirmed by fourier transform infrared (FTIR) spectrometry, proton nuclear magnetic resonance (1H-NMR) spectrometry and melt temperature determination. And then PEGDMA2000 was synthesized from PEG2000, and was affirmed by FTIR spectrometry, 1H-NMR spectrometry.Star-shaped oligo[(D,L-lactide)-co-ε-caprolactone] (PCLA) with different number-average molecular weights andε-caprolactone content was synthesized through ring-opening polymerization of D,L-lactide andε-caprolactone with dibutyl tin oxide (DBTO) or stannous octoate (Sn(oct)2) as catalyst and pentaerythritol as an initiator. The obtained oligomers were characterized by Fourier transform infrared spectrometry (FTIR), gel permeation chromatography (GPC) and ~1H proton nuclear magnetic resonance (1HNMR) spectrometry.Shape-memory IPNs materials were obtained through photopolymerization of PCLA and PEGDMA first and then thermal polymerization at 80℃.The hydrophilicity and transition temperatures of IPNs can be conveniently adjusted by changing the molecular weight of PCLA, the proportion ofε-caprolactone in the PCLA and the proportion of PEGDMA. The synthesis and characterization of the IPNs were also studied using FTIR, 1H-NMR and DSC.The degradation behavior of the IPNs was investigated in phosphate-buffered saline (pH=7.0) at 37℃by examining changes in weight loss and water absorption of the IPNs materials during the degradation. The results showed that, during the degradation, weight loss and water absorption increased gradually, which were mainly influenced by the molecular weight of PCLA, the ratio of D,L-lactide andε-caprolactone and the weight content of PEG associated with the IPNs.Furthermore, the mechanical properties were investigated by uniaxial drawing investigation. The results showed that the all IPNs posessed good mechanical strengths which could satisfy the need of special medical application.