Preparation and Chiral Recognition of Thermosensitive Poly（N-isopropylacrylamide） Microgels Containing Modified L-Phenylalanine Groups

Thermosensitive poly[N-isopropylacrylamide（NIPAM）-co-N-acryloyl-L-phenylalanine ethyl ester （NALPE）] microgels were prepared by the free radical polymerization of NIPAM and chiral monomer, NALPE. Such microgels exhibited spherical shape and favorable monodispersity. Increasing the content of NALPE units would en- hance the average diameter, but decrease the thermosensitivity and volume-phase transition temperatures of the mi- crogels. Compared with PNIPAM microgels, the microgels containing NALPE units performed chiral recognozable capacities for D-phenylalanine and D-tartaric acid, and the enantioselectivity and adsorption capacity of the microgels improved with increasing the temperature and/or the content of NALPE units.

Thermo-sensitive Poly(DEGMMA-co-MEA) Microgels: Synthesis, Characterization and Interfacial Interaction with Adsorbed Protein Layer

The novel microgels, poly[di（ethylene glycol） methyl ether methacrylate-co-2-methoxyethyl acrylate] poly（DEGMMA-co-MEA） microgels, were synthesized. The poly（DEGMMA-co-MEA） microgels were thermo-sensitive and exhibited a volume phase transitive temperature（VPTT） of 14–22 ℃. The incorporation of hydrophobic comonomer MEA shifted the VPTT of poly（DEGMMA-co-MEA） microgels to lower temperatures. The interfacial interaction of poly（DEGMMA-co-MEA） microgels and three model proteins, namely fibrinogen, bovine serum albumin and lysozyme, was investigated by quartz crystal microbalance（QCM）. An injection sequence of ＂microgel-after-protein＂ was then established for the real-time study of the interaction of proteins and the microgels at their swollen and collapsed states by using QCM technique. The results indicated that the interfacial interaction of poly（DEGMMA-co-MEA） microgels and adsorbed protein layers was mainly determined by the electrostatic interaction. Because poly（DEGMMA-co-MEA） microgels were negatively charged in Tris-HCl buffer solution（pH = 7.4）, the microgels did not adsorb on negatively charged fibrinogen and bovine serum albumin layers but strongly adsorbed on positively charged lysozyme layer. Stronger interaction between lysozyme and the microgels at collapsed state（i.e. at 37 ℃） was observed. Furthermore, the incorporation of MEA might weaken the interaction between poly（DEGMMA-co-MEA） microgels and proteins.

Conformation and Counterion Distribution of Polyelectrolyte in Solution as Viewed from Dielectric Approach

Polyelectrolyte solutions are more variable than uncharged macromolecule due to electrical interaction between charged molecules and surrounding counterions.Therefore,the subject of polyelectrolyte solutions has attracted a wide range of interests in both basic and applied research,and has also been extensively explored.However,the understanding of the molecular dynamics and conformation of polyelectrolytes in solution remains to be deepened,and universal consensus on some key issues have not been reached.Many methods have contributed to solving the above problems in different ways,including dielectric relaxation spectroscopy(DRS).In this perspective,we briefly reviewed the history of dielectric spectroscopic research on polyelectrolyte solution,with emphasis on summarizing our efforts.In particular,we expound the characteristics of DRS and its ability to obtain the internal information of the system of interest.Finally,we evaluate the advantages and limitations of the dielectric method and discussed future prospects of this field.