Abstract
The aim of the present work is to investigate the effect of various salts such as NaCl, KCl, NaBr, KBr, NaNO3, Na2SO4, and Na3PO4 as additives on the phase behavior of nonionic polymer hydroxypropylmethyl cellulose, HPMC. The cloud point of HPMC has been found to be induced by the addition of above salts. On the basis of cloud point values obtained at different [HPMC], the energetics of the clouding process have been calculated. It was found that in the presence of salts the cloud point (T-CP) of HPMC decreased almost linearly with the salt concentration dependent on the type of salt used. Further, it was observed that the T-CP decreases on increasing HPMC concentration at a fixed salt concentration, followed by minima except for NaCl and Na3PO4 for which T-CP increases slightly after achieving a minimum value. Also, the free energy of clouding (Delta G(c)) becomes less negative indicating that the process is becoming energetically less favorable on increasing the polymer concentration.