SINGLE-CHAIN CONFORMATION FOR INTERACTING POLY(N-ISOPROPY ACRYLAMIDE) IN AQUEOUS SOLUTION
作者：Boualem Hammouda;* Di Jia; He Cheng
關(guān)鍵字：water soluble polymer, configuration, water
論文來源：期刊
具體來源：the Open Access Journal of Science and Technology
發(fā)表時間：2015年
The demixing phase behavior of Poly(N-isopropylacrylamide) (PNIPAM) aqueous solution is investigated using smallangle
neutron scattering. This polymer phase separates upon heating and demixes around 32 °C. The pre-transition temperature
range is characterized by two scattering modes; a low-Q (large-scale) signal and a high-Q dissolved chains signal. In order to get
insight into this pre-transition region, especially the origin of the low-Q (large-scale) structure, the zero average contrast method
is used in order to isolate single-chain conformations even in the demixing polymers transition region. This method consists of
measuring deuterated and non-deuterated polymers dissolved in mixtures of deuterated and non-deuterated water for which the
polymer scattering length density matches the solvent scattering length density. A fixed 4% polymer mass fraction is used in a
contrast variation series where the d-water/h-water fraction is varied in order to determine the match point. The zero average
contrast (match point) sample displays pure single-chain scattering with no interchain contributions. Our measurements prove that
the large scale structure in this polymer solution is due to a transient polymer network formed through hydrophobic segmentsegment
interactions. Scattering intensity increases when the temperature gets close to the phase boundary. While the apparent
radius of gyration increases substantially at the Lower Critical Solution Temperature (LCST) transition due to strong interchain
correlation, the single-chain true radius of gyration has been found to decrease slightly with temperature when approaching the
transition.