Investigation of interpolymer complexation between Carbopol and various grades of polyvinylpyrrolidone and effects on adhesion strength and swelling properties.

PURPOSE To investigate the interpolymer complexation between Carbopol 934P (CP) and various grades of polyvinylpyrrolidone (PVP) (K90, K32, C15, and VA/S-630). METHODS Amount of fresh and dried CP-PVP complexes, water retaining capacity, apparent density, pH, conductivity, FTIR, swelling and adhesion strength were studied. RESULTS Interpolymer complexation occurred between CP and all the PVP, but most significantly with PVP K90. Maximum amount of fresh and dried CP-PVP K32 complexes were obtained at a weight ratio of 1:1. On the contrary, CP concentration was linearly related to amount of CP-PVP K90 complexes produced and their water retaining capacity were all above 97%. Increase in CP concentration caused a decrease in pH, but an increase in conductivity for all the CP-PVP complexes. The apparent density of the filtrate of CP-PVP K90 complex was the lowest and its IR spectrum was similar to that of pure PVP K90, indicating that all the CP has interacted with the PVP K90. Discs of physical mixtures of CP-PVP K90 swelled gradually and reached a maximum after 20-30 hr, while discs of solid complex swelled readily and reached a maximum within 20 hr. Adhesion strength was directly correlated to CP content. However, adhesion strength of solid CP-PVP K90 complex was lower than the physical mixture of the pure polymers. CONCLUSION Interpolymer complexation occurred between CP and PVP but to a different extent for the various grades of PVP. Complexation was most prominent between CP and PVP K90.