The Research Of Synthesis And Classification Of LCST Type Polymer And Its Aqueous Solution Phase Separation Process

In the active polymerization process,if the reaction conditions are appropriate,there will be no chain termination reaction and chain transfer reaction,which is known as the polymerization reaction.Compared with the traditional free radical polymerization,the active polymerization has the characteristics of no transfer,no termination,and the rate of initiation is much larger than the chain growth rate,it can better realize the control of molecular structure.It is an important means for the realization of molecular design and synthesis of polymers with specific structures and properties.In this paper,a kind of active polymerization method is adopted,it is called Reversible Addition-Fragmentation Chain Transfer Polymerization(RAFT).Through the design of molecular weight,the proportion of monomer,chain transfer agent and initiator,synthesized the samples of PNIPAM with different molecular weight and narrow molecular weight distribution.Using the method of stepwise precipitation,with toluene as solvent,petroleum ether as precipitating agent,classificationed the sample of PVME with different molecular weight and molecular weight distribution.Characterizated each product with FT-IR and GPC,the results showed that the target product with a clear structure and narrow molecular weight distribution was successfully synthesized or graded,laying the foundation for the back test.The phase separation behavior of polymer solution system has been a hot research topic in the polymer field.Many scholars have studied it and have achieved good results.In this paper,differential scanning calorimetry was used to test the water solution of the synthesized and graded samples,found that the second phase separation enthaipy includes two parts:Hydrogen bond interaction between polymer and water molecules and the swelling effect of water molecules on polymer.The former one does not change with the change of the isothermal time,corresponding to the lower platform of the second phase separation enthalpy;The latter begins to increase rapidly with the increase of the isothermal time,and finally reached a stable value,meanwhile,this study focused on the molecular weight dependence of the molecular weight of the polymer samples in the phase separation process.