Department of Chemical and Life Science Engineering, Virginia Commonwealth University, 601 West Main Street, Richmond, Virginia 23284, USA.
Langmuir. 2010 Jun 1;26(11):9032-9. doi: 10.1021/la904849u.
Prior research established that P[AB]-copolyoxetane polyurethanes with soft blocks having A = trifluoroethoxy (CF(3)CH(2)-O-CH(2)-, 3FOx) and B = dodecylammonium-butoxy (C12) are highly effective as polymer surface modifiers (PSMs). These PSMs displayed high contact antimicrobial efficiency against spray challenge that was attributed to surface concentration of quaternary charge. Herein, using a novel cell design and polymer coating process, streaming potential (SP) measurements are reported for estimating accessible surface charge density. Fused-silica capillaries were embedded in flat polypropylene sheets, and the inner capillary walls were coated with neat HMDI-BD(30)-P[(3FOx)(C12)-87:13-5100] (PU-1) and 1 wt % PU-1 in HMDI-BD(50)-PTMO-1000 (base polyurethane 2). Effects of annealing (60 degrees C) and electrolyte flow cycles on near-surface quaternary charge concentration were determined. Neat PU-1 had a constant SP that was cycle-independent and actually increased on annealing. As-cast 1 wt % PU-1 showed initial SPs about half those for neat PU-1, with substantial attenuation over 16 measurement cycles. SPs for annealed 1 wt % PU-1 displayed lower initial values that attenuated rapidly over multiple cycles. Zeta potentials and surface charge densities were calculated from SPs and discussed relative to contact antimicrobial properties. Tapping mode atomic force microscopy (TM-AFM) imaging was employed for investigation of 1 wt % PU-1 surface morphology. Microscale phase separation occurs on annealing 1 wt % PU-1 for 24 h at 60 degrees C. Surprisingly, phase separation was also observed after short immersion of 1 wt % PU-1 coatings in water. The morphological changes are correlated with instability of near-surface charge found by SP measurements. A model is proposed for near-surface spinodal decomposition of metastable as-cast 1 wt % PU-1. The formation of a fluorous modifier rich phase apparently sequesters near-surface quaternary charge and accounts for temporal instability of antimicrobial properties. The results are important in providing a facile method for screening polycation-based, contact antimicrobial coatings for accessible charge density and in assessing durability.
先前的研究已经确定，具有软段 A = 三氟乙氧基（CF3CH2-O-CH2，3FOx）和 B = 十二烷基铵-丁氧基（C12）的 P[AB]-共聚氧杂环丁烷型聚氨酯是非常有效的聚合物表面改性剂（PSM）。这些 PSM 在喷雾挑战中表现出很高的接触抗菌效率，这归因于表面的季铵电荷浓度。在此，使用新型的细胞设计和聚合物涂层工艺，报告了用于估计可及表面电荷密度的流动电势（SP）测量。熔融石英毛细管嵌入在平面聚丙烯片中，并且内毛细管壁用纯 HMDI-BD（30）-P[（3FOx）（C12）-87：13-5100]（PU-1）和 1wt%PU-1 在 HMDI-BD（50）-PTMO-1000（基础聚氨酯 2）涂覆。确定了退火（60°C）和电解质流动循环对近表面季铵电荷浓度的影响。纯 PU-1 具有与循环无关的恒定 SP，并且在退火时实际上增加。铸态 1wt%PU-1 显示初始 SP 约为纯 PU-1 的一半，经过 16 次测量循环后衰减很大。退火 1wt%PU-1 的 SP 初始值较低，在多个循环中迅速衰减。从 SP 计算了 Zeta 电位和表面电荷密度，并与接触抗菌性能进行了讨论。使用原子力显微镜（TM-AFM）成像对 1wt%PU-1 表面形貌进行了研究。在 60°C 下退火 1wt%PU-1 24 小时会发生微相分离。令人惊讶的是，在将 1wt%PU-1 涂层短时间浸入水中后也观察到了相分离。形态变化与 SP 测量发现的近表面电荷的不稳定性相关。提出了一种用于亚稳铸态 1wt%PU-1 近表面旋节分解的模型。富氟修饰剂相的形成显然隔离了近表面季铵电荷，并解释了抗菌性能的时间不稳定性。这些结果对于提供一种简便的方法来筛选基于聚阳离子的接触抗菌涂层以获得可及电荷密度以及评估耐久性非常重要。
