Niebuur Bart-Jan, Puchmayr Jonas, Herold Christian, Kreuzer Lucas P, Hildebrand Viet, Müller-Buschbaum Peter, Laschewsky André, Papadakis Christine M
Physik-Department, Fachgebiet Physik weicher Materie/Lehrstuhl für Funktionelle Materialien, Technische Universität München, 85748 Garching, Germany.
Institut für Chemie, Universität Potsdam, 14476 Potsdam-Golm, Germany.
Materials (Basel). 2018 May 21;11(5):850. doi: 10.3390/ma11050850.
Polysulfobetaines in aqueous solution show upper critical solution temperature (UCST) behavior. We investigate here the representative of this class of materials, poly (,-dimethyl--(3-methacrylamidopropyl) ammonio propane sulfonate) (PSPP), with respect to: (i) the dynamics in aqueous solution above the cloud point as function of NaBr concentration; and (ii) the swelling behavior of thin films in water vapor as function of the initial film thickness. For PSPP solutions with a concentration of 5 wt.%, the temperature dependence of the intensity autocorrelation functions is measured with dynamic light scattering as function of molar mass and NaBr concentration (0⁻8 mM). We found a scaling of behavior for the scattered intensity and dynamic correlation length. The resulting spinodal temperatures showed a maximum at a certain (small) NaBr concentration, which is similar to the behavior of the cloud points measured previously by turbidimetry. The critical exponent of susceptibility depends on NaBr concentration, with a minimum value where the spinodal temperature is maximum and a trend towards the mean-field value of unity with increasing NaBr concentration. In contrast, the critical exponent of the correlation length does not depend on NaBr concentration and is lower than the value of 0.5 predicted by mean-field theory. For PSPP thin films, the swelling behavior was found to depend on film thickness. A film thickness of about 100 nm turns out to be the optimum thickness needed to obtain fast hydration with H₂O.
聚磺基甜菜碱在水溶液中表现出上临界溶液温度（UCST）行为。我们在此研究这类材料的代表物聚（2,2-二甲基-2-（3-甲基丙烯酰胺丙基）铵丙烷磺酸盐）（PSPP），涉及以下方面：（i）浊点以上水溶液中的动力学随溴化钠浓度的变化；（ii）薄膜在水蒸气中的溶胀行为随初始膜厚度的变化。对于浓度为5 wt.%的PSPP溶液，通过动态光散射测量强度自相关函数的温度依赖性，作为摩尔质量和溴化钠浓度（0⁻8 mM）的函数。我们发现散射强度和动态相关长度的行为存在标度关系。所得的旋节线温度在某一（较小）溴化钠浓度处出现最大值，这与之前通过比浊法测量的浊点行为相似。磁化率的临界指数取决于溴化钠浓度，在旋节线温度最大处有最小值，且随着溴化钠浓度增加有趋向于平均场值1的趋势。相比之下，相关长度的临界指数不依赖于溴化钠浓度，且低于平均场理论预测的0.5值。对于PSPP薄膜，发现溶胀行为取决于膜厚度。结果表明，约100 nm的膜厚度是与水快速水合所需的最佳厚度。
