Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, Colorado 80523-1370, USA.
Biomacromolecules. 2011 Jul 11;12(7):2755-65. doi: 10.1021/bm200519y. Epub 2011 Jun 15.
Polyelectrolyte multilayers using the polycations chitosan and N,N,N-trimethyl chitosan and the polyanions hyaluronan, chondroitin sulfate, and heparin are studied. Chitosan and hyaluronan behave as a weak polycation and weak polyanion, respectively, whereas N,N,N-trimethyl chitosan, chondroitin sulfate, and heparin behave as strong polyelectrolytes. Hydrophilicity is determined by water contact angle measurements and by comparing wet and dry film thickness measurements. Wet thickness is obtained using Fourier transform surface plasmon resonance, whereas dry thickness is obtained through ellipsometry. For the very thin PEMs studied here, the surface hydrophilicity and swelling in water are highly correlated. The multilayer chemistry is assessed by FT-IR and X-ray photoelectron spectroscopy (XPS). FT-IR and XPS provide information about the composition, degree of ionization, and by inference, the ion pairing. We find that hydrophilicity and swelling are reduced when one polyelectrolyte is strong and the other is weak, whereas ion pairing is increased. By this combination of techniques, we are able to compose a unified description of how the PEM swelling is dictated by the ion pairing in thin polysaccharide-based PEMs.
使用聚阳离子壳聚糖和 N,N,N-三甲基壳聚糖以及阴离子透明质酸、硫酸软骨素和肝素的聚电解质多层被研究。壳聚糖和透明质酸分别表现为弱聚阳离子和弱聚阴离子，而 N,N,N-三甲基壳聚糖、硫酸软骨素和肝素则表现为强聚电解质。亲水性通过水接触角测量和比较湿膜和干膜厚度测量来确定。湿膜厚度通过傅里叶变换表面等离子体共振（FT-IR）获得，而干膜厚度通过椭圆偏光法（ellipsometry）获得。对于这里研究的非常薄的 PEM，表面亲水性和在水中的溶胀高度相关。多层化学性质通过傅里叶变换红外光谱（FT-IR）和 X 射线光电子能谱（XPS）进行评估。FT-IR 和 XPS 提供了关于组成、离解度以及推断的离子配对的信息。我们发现，当一种聚电解质强而另一种聚电解质弱时，亲水性和溶胀性降低，而离子配对增加。通过这种组合技术，我们能够对多糖基 PEM 中 PEM 溶胀如何由离子配对决定进行统一描述。
