The Homogeneous Recovery Process Of Amphiphilic Polymer Aqueous Solution

It is well known that acrylamide, polyvinyl alcohol and other amphiphilic polymers are polymers which have a lower critical solution temperature(LCST) in aqueous solution. Below LCST, these polymers are soluble in water, with the form of coil. However, if heated above the LCST, they will separate as a result of the balance and competition effect between hydrogen bond and hydrophobic hydration.Adopting differential scanning calorimetry to examine the poly(vinyl methyl ether)(PVME) solution with different water content, we found the second phase separation enthalpy of the system includes two parts: 1. the hydrogen bonding between polymer and water molecules. 2. The effect of water molecules on swelling of polymer. The former part does not vary with the change of the isothermal time, corresponding with the lower platform of the phase separation enthalpy. The latter part increases rapidly with the increase of isothermal time in 120 min range and eventually reaches a stable value.The homogeneous recovery process of PVME aqueous solution has been studied by Fourier transform infrared spectra and steady-state fluorescence spectra. It is found that the interaction of water molecules and polymers is fast in the homogeneous recovery process, and there is no weak interaction of time dependence.Poly(N-isopropylacrylamide)(PNIPAM) and poly(2-(2-methoxyethoxy)ethyl methacrylate)(PMEO2MA) with different molecular weight were synthesized by RAFT polymerization. GPC analysis indicates that the synthesized polymers have narrow molecular weight distribution. Moreover, the test results of thermodynamic show that different thermodynamic processes have a certain influence on the second phase separation enthalpy value for PNIPAM and PMEO2 MA aqueous solution. However, the impact isn't significant. Amide and ether oxygen in polymers which interact with water molecules, are more complex, far away from the main chain in the homogeneous recovery process. As a result, the impact on the molecular chain collapse effect is not significant.