Hofmeister series and Collins' model were used to explain the results.
The numbers of papers involved in Hofmeister series related to various fields especially biomedicine are large and still keep growing everyyear [8-10].
The order of [K.sup.+] > [Na.sup.+] > [Mg.sup.2+] > [Ca.sup.2+] was mentioned in Hofmeister series, which was followed on the efficiency of cations as salting-out agents.
Addition of Hofmeister series of salts enhances the formation of complex between PVA-PSSNa which in turn decreases the LCST of mixture of polymers.
The decrease of the LCST is in the order Na2SO4 (less than) NaF (less than) NaCl (less than) NaClO3 (less than) NaNO3 (less than) NaBr (less than) NaSCN which is opposite to classical Hofmeister series. Chaotropic anions favour the formation of complex more than kosmotropic anions this is because chaotropes have low surface tension values as compared to kosmotropes which lead to strengthening of hydrophobic interaction and enhances the complex formation which in turn shift the LCST toward lower temperature.
Key words: Poly (vinyl alcohol), Poly (Sodium 4-Styrene Sulphonate), LCST, phase separation and Hofmeister series.
The influence of inorganic aqueous salt solutions on synthetic or natural hydrophilic polymeric materials can be deduced from the Hofmeister series. According to Hofmeister series, ions are either kosmotropic (they tend to destabilize the hydrogen bonds between water molecules or between water and polymeric chains leading to a collapsing of the polymeric network) or chaotropic (they tend to stabilize the hydrogen bonds in hydrophilic polymers leading to polymeric matrix swelling) (Bagger et al.
The swelling degree of [C.sub.1] is higher, due to the kosmotropic effect of N[H.sub.4.sup.+] ion (according to the Hofmeister series) which tends to break the hydrogen bonds between the water molecules, water and polymer molecules and between the polymeric chains, leading to an increased swelling of the cryogel.
Looking for possible effects of counterions, I selected perchlorate as a chloride substitute because it is near the end of the Hofmeister series
, which ranks ion effects on soluble proteins (6).
The Hofmeister series (23) ranks the tendency of different salts to perturb the denaturation temperature of proteins.
The effect of ions of the Hofmeister series on the LCST of IPAM-100 (24) is discussed in the accompanying paper (8).