Salt acts as a plasticizer in polyelectrolyte complexes (PECs), which impacts the physical, thermal, and mechanical properties, thus having implications in applications, such as drug delivery, energy storage, and smart coatings. Added salt disrupts polycation–polyanion intrinsic ion pairs, lowering a hydrated PEC’s glass transition temperature (T_g). However, the relative influence of counterion type on the PEC’s T_g is not well understood. Here, the effect of anion type (NaCl, NaBr, NaNO₃, and NaI) on the T_g of solid-like, hydrated PECs composed of poly(diallydimethylammonium) (PDADMA)–poly(styrenesulfonate) (PSS) is investigated. With increasing the chaotropic nature of the salt anion, the T_g decreases. The relative differences are attributed to the doping level, the amount of bound water, the mobility of water molecules within the PECs, and the strength of interactions between the PEs. For all studied salt concentrations and salt types, the T_g followed the scaling of −1/T_g ≈ ln([IP]/[H₂O]), in which [IP]/[H₂O] is the ratio of intrinsic pairs to water. The scaling estimates that about 7 to 17% of the intrinsic ion pairs should be weakened for the PEC to partake in a glass transition. Put together, this study highlights that the T_g in PECs is impacted by the salt anion, but the mechanism of the glass transition remains unchanged.

中文翻译：

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抗衡阴离子类型影响聚电解质复合物的玻璃化转变温度


盐在聚电解质复合物 (PEC) 中充当增塑剂，影响物理、热和机械性能，从而对药物输送、能量存储和智能涂层等应用产生影响。添加的盐会破坏聚阳离子-聚阴离子的固有离子对，降低水合 PEC 的玻璃化转变温度 (T _g )。然而，反离子类型对 PEC T _g 的相对影响尚不清楚。此处，阴离子类型（NaCl、NaBr、NaNO ₃ 和 NaI）对由聚（二烯丙基二甲基铵）（PDADMA）组成的固体状水合 PEC 的 T _g 的影响–研究了聚（苯乙烯磺酸）（PSS）。随着盐阴离子离液性质的增加，T _g 降低。相对差异归因于掺杂水平、结合水量、PEC 内水分子的迁移率以及 PE 之间相互作用的强度。对于所有研究的盐浓度和盐类型，T _g 遵循 −1/T _g ≈ ln([IP]/[H ₂ O ]），其中[IP]/[H ₂ O]是本征对与水的比率。缩放估计大约 7% 到 17% 的固有离子对应该被削弱，以便 PEC 参与玻璃化转变。综上所述，本研究强调 PEC 中的 T _g 受到盐阴离子的影响，但玻璃化转变的机制保持不变。