Litwinowicz Matthew, Rogers Sarah, Caruana Andrew, Kinane Christy, Tellam James, Thompson Richard
Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom.
STFC ISIS Facility, Rutherford Appleton Laboratories, Chilton, Didcot OX11 0QX, United Kingdom.
Macromolecules. 2021 Oct 26;54(20):9636-9648. doi: 10.1021/acs.macromol.1c01600. Epub 2021 Oct 6.
The elastic modulus and hydrophilicity of cross-linked poly(dimethylsiloxane) (PDMS) are tunable via cross-linker concentration and the addition of a simple surfactant, CE, before curing. However, the surfactant concentration, [CE], reduces the elastic modulus (73% lower for 6.3% w/w) because it reduces the extent of curing. This is likely because the hygroscopic surfactant results in water poisoning of the catalyst. Three distinct time-dependent hydrophilicity profiles were identified using water contact angle analysis with [CE] determining which profile was observed. This indicates the concentration-dependent phase behavior of CE within PDMS films. Changes in phase behavior were identified using small-angle neutron scattering (SANS) and a compatibility study. No surface excess or surface segregation of surfactant was observed at the PDMS-air interface. However, a surface excess revealed by neutron reflectivity against a DO interface indicates that the increase in hydrophilicity results from the migration of CE to the film interface when exposed to water.
交联聚二甲基硅氧烷（PDMS）的弹性模量和亲水性可通过交联剂浓度以及在固化前添加一种简单的表面活性剂CE来调节。然而，表面活性剂浓度[CE]会降低弹性模量（对于6.3% w/w的情况降低73%），因为它会降低固化程度。这可能是因为吸湿性表面活性剂导致催化剂发生水毒化。通过水接触角分析确定了三种不同的随时间变化的亲水性曲线，[CE]决定观察到哪种曲线。这表明CE在PDMS薄膜中的浓度依赖性相行为。使用小角中子散射（SANS）和相容性研究确定了相行为的变化。在PDMS-空气界面未观察到表面活性剂的表面过量或表面偏析。然而，相对于DO界面的中子反射率显示的表面过量表明，亲水性的增加是由于CE在接触水时迁移到薄膜界面所致。
