Ionic species are important to dominate phase separation behaviors of poly(N-isopropylacrylamide) (PNIPAm) in aqueous solutions. Herein, photoresponsive azobenzene-based salts with various ions are prepared and their photoresponsive ion effects on clouding temperatures (T_cpS) of PNIPAm in aqueous solutions are explored. It is found that, despite of various structures of anions and cations, trans-T_cpS under vis light irradiation are always higher than cis-T_cpS under UV irradiation. Particularly, Hofmeister effect of anions on T_cpS is roughly observed. For example, azobenzene with kosmotropic CO₃²⁻ gives the lowest cis-T_cp while in use of typical chaotropic anions, such as ClO₄⁻, azobenzene isomerization less affects values of T_cps. In another hand, azobenzene-based metallic salts containing lithium, sodium, and potassium cations also demonstrate photoresponsive Hofmeister effect. Trans-metallic azobenzene demonstrates a chaotropic effect on T_cps while UV induces kosmotropic behaviors on T_cpS. Additionally, ionic conduction of the solution along with photoresponsive phase separations is also investigated and PNIPAm aggregations induce a sharp reduction of ion conduction during UV light illumination.

中文翻译：

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偶氮苯盐对水溶液中 PNIPAm 光响应的特定离子效应

离子物质对于控制聚（N-异丙基丙烯酰胺）（PNIPAm）在水溶液中的相分离行为很重要。在此，制备了具有各种离子的光响应性偶氮苯基盐，并探讨了它们的光响应性离子对水溶液中 PNIPAm混浊温度 ( T _cpS ) 的影响。据发现，尽管阴离子和阳离子的各种结构中，反式- Ť _CPS VIS光照射下比总是更高的顺式- Ť _CPS紫外光照射下。特别是，大致观察到阴离子对T _{cpS 的}霍夫迈斯特效应。例如，具有亲液性 CO 的偶氮苯₃ ^2-给出最低顺- Ť _CP，而在使用典型的离液阴离子，如CLO的₄ ^{- ，}偶氮苯异构化较少影响的值Ť _CP秒。另一方面，含有锂、钠和钾阳离子的偶氮苯基金属盐也表现出光响应霍夫迈斯特效应。反式金属偶氮苯对T _cp s表现出离液效应，而紫外线则对T _cpS诱导亲液行为. 此外，还研究了溶液的离子传导以及光响应相分离，并且 PNIPAm 聚集会导致紫外光照射期间离子传导的急剧减少。