Self-Exchange of Polyelectrolyte in Multilayers: Diffusion as a Function of Salt Concentration and Temperature
Self-Exchange of Polyelectrolyte in Multilayers: Diffusion as a Function of Salt Concentration and Temperature
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DOI：
10.1021/acs.macromol.1c01464
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发表时间：
2021-10-13
期刊：
影响因子：
5.5
通讯作者：
Schlenoff, Joseph B.
中科院分区：
文献类型：
--
作者：
Abbett, Rachel L.;Chen, Yuhui;Schlenoff, Joseph B.
用逐层法制备的S超薄膜测量了水合聚电解质复合体中的高分子链扩散。D窄分子量分布聚二烯丙基二甲基铵(PDADMA)作为PEC的聚阳离子。对起始膜进行了广泛的前处理，以消除残余应力、各向异性和分层。PSS/PDADMA“多层膜”PEMU足够薄，可以提供大量的聚电解质交换，即使扩散系数低至10(-16)cm(2)S(-1)，作为盐浓度和温度的函数，测量了这种PEC的玻璃化转变温度T-g，接近室温。两个分子量分别约为15 kDa和100 kDa的DPSS在较高的温度下扩散较快，其活化能分别约为21和53kJ mol(-1)，后者与两对PSS：PDADMA之间的位置交换的活化能E-a大致相同。对宏观PECS的线性粘弹性响应的研究表明，与相同的PDADMA络合的两段PSS的T-g相差约8℃。在室温下，增加盐浓度对100 kDa PSS的D有影响，但对15 kDa PSS的D影响不大。D在靠近溶液界面的膜层区域较快，这也归因于该界面处较大的水含量导致较低的T-g。
Polymer chain diffusion within a hydrated polyelec- trolyte complex, PEC, has been measured using an ultrathin film S format prepared by the layer-by-layer method. Isotopically labeled self-exchange of deuterated polystyrene sulfonate), dPSS, with undeuterated PSS of the same narrow molecular weight distribution permitted reliable estimates of whole-molecule diffusion coefficients, D. Narrow molecular weight distribution poly- (diallyldimethylammonium), PDADMA, was used as the polycation for the PEC. Extensive pretreatment of starting films was undertaken to remove residual stress, anisotropy, and layering. PSS/PDADMA "multilayers," PEMUs, thin enough to provide substantial exchange of polyelectrolyte, even with diffusion coefficients as low as 10(-16) cm(2) s(-1), as a function of salt concentration and temperature were measured for this PEC, which has a glass-transition temperature, T-g, close to room temperature. Two molecular weights of dPSS, about 15 and 100 kDa, presumed to be below and above the entanglement molecular weight, respectively, both diffused faster at higher temperatures with respective activation energies, E-a of about 21 and 53 kJ mol(-1), the latter about the same as E-a for the place exchange between two pairs of PSS:PDADMA. Studies of the linear viscoelastic response of macroscopic PECs showed a difference of about 8 degrees C in the T-g of the two lengths of PSS complexed with the same PDADMA. Increasing concentrations of NaCl influenced D of 100 kDa PSS but not 15 kDa PSS at room temperature. D was faster in the region of the film near the solution interface, again attributed to a lower T-g caused by greater water content at this interface.