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利用超灵敏微量差示扫描量热仪(US-DSC),研究了聚(N-异丙基丙烯酰胺)(PNIPAM)在稀溶液和亚浓溶液中的折叠与聚集.随温度的升高,在稀溶液中,PNIPAM链同时发生链内折叠与链间聚集,而且链内折叠所占的比重随浓度的降低而变大.在亚浓溶液中,PNIPAM链在低温下已经塌缩,当温度升高时,PNIPAM链只发生有限的链间聚集.在极稀溶液中,PNIPAM链随温度升高而发生单链折叠.通过浓度和加热速率外推至0,得到了PNIPAM单链折叠的焓变,该焓变高于链间聚集的焓变,说明高分子单链折叠不同于宏观相变.
The folding and aggregation of poly (N-isopropylacrylamide) (PNIPAM) in dilute and sub-concentrated solutions were investigated by means of ultra-sensitive micrometre differential scanning calorimetry (US-DSC) In dilute solution, the PNIPAM chains are simultaneously aggregated within the chain and between chains, and the proportion of the chain within the fold becomes larger as the concentration decreases. In the sub-concentrated solution, the PNIPAM chains have collapsed at low temperatures, In the very dilute solution, PNIPAM chains undergo single-strand folding with increasing temperature, extrapolation to zero by concentration and heating rate gives the enthalpy of PNIPAM single-stranded folding The enthalpy change is higher than that of the enthalpy change between the chains, indicating that the polymer single-stranded folding is different from the macroscopic phase transition.