Influence of Hydrogen Bonding on the Temperature-Accelerated Hydrolysis of Silicone Based Polyetherurethane

Temperature-accelerated in vitro degradation was established to estimate the longevity of polyurethane applied for long-term implantation.However,the prediction did not correlate well with the data from clinical explants and the rationality of accelerated in vitro test is still in a controversial due to the deviation.To improve the accuracy of the in vitro prediction,the influence of hydrogen bonding(HB)on the accelerated hydrolysis of silicone based polyetherurethans(SPEUs)extended with three side chains.Combining the temperature-controlled FTIR and the physical properties after temperature-accelerated in vitro degradation,it was demonstrated that side chain could increase the degree of hydrogen bond dissociation at higher temperature,resulting in the decrease of the calculated activation energy(E_(a))of hydrolysis.At low temperatures,changes in surface morphology and molar mass of PEUs are minimal and HB are less easily dissociated,which had barely impact on the hydrolysis resistance.It was proposed that the E_(a) will not be impacted and that the accuracy of prediction will be increased if the acceleration temperature is lower than 70℃ and HB change is less than 15%.

Effect of Fluorocarbon Side Chain on the Microphase Morphology and Rheological Behavior of Thermoplastic Polyurethanes

Fluorinated diols(FDO)with dangling chain were introduced into polyether urethanes(PEUs)as chain extender in order to achieve internal plasticization.Based on temperature dependent Fourier transform infrared(FTIR)spectroscopy results,the fluorinated polyether urethanes(FPEUs)exhibited weaker hydrogen bonding between C=O and N―H groups with addition of FDO.The crystallinity of hard domain was destroyed determined by thermal analysis.Combined with the results of dynamic mechanical analysis(DMA)and dissipative particle dynamics(DPD)simulation,it was proved that more loosely aggregated hard domains with weakened interaction separated from soft segment were formed.Rheological analysis indicated that FDO reduced the complex viscosity and viscous flow activation energy which endowed the polymer with more flexibility.Despite the loss of hydrogen bonds,there was no significant decline in mechanical property resulting from the decrease of hard segment dissolved in soft segment phase.The presence of fluorinated carbon side chain could function as internal plasticizer and contribute to the processability of polyurethane.