Poly(N-vinylcaprolactam) microgels and its related composites

Spherical hydrogels were prepared by precipitation copolymerization of N-vi nylcaprolactam and sodium acrylate [P(VCL-co-NaA)] at 60 degreesC. As a the rmally sensitive polymer, the increase of temperature in the range 25-40 de greesC can lead to a continuous shrinking of PVCL homopolymer chains. The c opolymerization of a few molar percent of NaA. into a PVCL chain increases its swelling extent and shifts its shrinking temperature slightly higher. O ur results revealed that in the shrinking process, calcium ions (Ca2+) indu ced a profound complexation of the P(VCL-co-NaA) microgels at a critical te mperature (T-c) which was nearly independent of the NaA content. However, b oth the rate and degree of the complexation increase as the NaA content inc reases at T-c. One the basis of this study, we further studied the complexa tion of P(VCL-co-NaA) microgels with gelatin in the presence of calcium ion s and prepared chemically crosslinked of the gelatin gels with embedded P(V CL-co-NaA) microgels. Our results showed that the shrinking of the embedded P(VCL-co-NaA) microgels could lead to the shrinking of gelatin gels. The b iomedical application of this gelatin/microgel composite have been exploite d.