Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843-3122, USA.
Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, USA.
J Chem Phys. 2018 Oct 28;149(16):163317. doi: 10.1063/1.5037491.
The influence of assembly and post-assembly conditions on the glass transition temperature of free-standing poly(diallyldimethyl ammonium) (PDADMA)/poly(4-styrene sulfonate) (PSS) layer-by-layer (LbL) films assembled in 0.5M NaCl and 0.5M KBr are explored using modulated differential scanning calorimetry. Upon completion, PDADMA/PSS LbL assemblies are hydrated using solutions containing various concentrations of KBr. The data indicate that water provides the primary driving force for changes in the glass transition temperature of completed films rather than the post-assembly salt type. However, upon changing the assembly salt conditions from NaCl to KBr, the glass transition temperature shows a decrease of nearly 20 °C. Additionally, the composition of the films upon analysis with H NMR spectroscopy and neutron activation analysis indicates an elevated number of extrinsic binding sites within the film structure when KBr is the assembly salt. This shows a clear link between the assembly conditions and the internal structure and, therefore, the thermal properties of PDADMA/PSS LbL assemblies.
采用调制差示扫描量热法研究了在 0.5M NaCl 和 0.5M KBr 中组装的自由支撑的聚二烯丙基二甲基铵（PDADMA）/聚 4-苯乙烯磺酸盐（PSS）层层（LbL）膜的组装和后组装条件对玻璃化转变温度的影响。完成后，使用含有不同浓度 KBr 的溶液对 PDADMA/PSS LbL 组装体进行水合。数据表明，水是完成膜玻璃化转变温度变化的主要驱动力，而不是后组装盐的类型。然而，当将组装盐条件从 NaCl 更改为 KBr 时，玻璃化转变温度显示出近 20°C 的下降。此外，通过 H NMR 光谱和中子活化分析对膜进行分析表明，当 KBr 为组装盐时，膜结构内存在更多的外在结合位点。这表明组装条件与内部结构之间存在明显联系，因此也与 PDADMA/PSS LbL 组装体的热性能有关。
