Sudre Guillaume, Siband Elodie, Gallas Bruno, Cousin Fabrice, Hourdet Dominique, Tran Yvette
Ingénierie des Matériaux Polymères, Université Claude Bernard Lyon 1, Université de Lyon, CNRS UMR 5223, 69100 Villeurbanne, France.
Soft Matter Sciences and Engineering, ESPCI Paris, PSL Université, Sorbonne Université, CNRS, 10 rue Vauquelin, F-75005 Paris, France.
Polymers (Basel). 2020 Jan 7;12(1):153. doi: 10.3390/polym12010153.
We investigate the adsorption of pH- or temperature-responsive polymer systems by ellipsometry and neutron reflectivity. To this end, temperature-responsive poly (-isopropylacrylamide) (PNIPAM) brushes and pH-responsive poly (acrylic acid) (PAA) brushes have been prepared using the "grafting onto" method to investigate the adsorption process of polymers and its reversibility under controlled environment. To that purpose, macromolecular brushes were designed with various chain lengths and a wide range of grafting density. Below the transition temperature (LCST), the characterization of PNIPAM brushes by neutron reflectivity shows that the swelling behavior of brushes is in good agreement with the scaling models before they collapse above the LCST. The reversible adsorption on PNIPAM brushes was carried out with linear copolymers of -isopropylacrylamide and acrylic acid, P(NIPAM--AA). While these copolymers remain fully soluble in water over the whole range of temperature investigated, a quantitative adsorption driven by solvophobic interactions was shown to proceed only above the LCST of the brush and to be totally reversible upon cooling. Similarly, the pH-responsive adsorption driven by electrostatic interactions on PAA brushes was studied with copolymers of NIPAM and ,-dimethylaminopropylmethacrylamide, P(NIPAM--MADAP). In this case, the adsorption of weak polycations was shown to increase with the ionization of the PAA brush with interactions mainly located in the upper part of the brush at pH 7 and more deeply adsorbed within the brush at pH 9.
我们通过椭偏仪和中子反射率研究了pH或温度响应性聚合物体系的吸附情况。为此，使用“接枝到”方法制备了温度响应性聚（N-异丙基丙烯酰胺）（PNIPAM）刷和pH响应性聚（丙烯酸）（PAA）刷，以研究聚合物在可控环境下的吸附过程及其可逆性。为此目的，设计了具有不同链长和广泛接枝密度的大分子刷。在转变温度（最低临界溶液温度，LCST）以下，通过中子反射率对PNIPAM刷进行表征表明，在刷在LCST以上塌陷之前，刷的溶胀行为与标度模型吻合良好。使用N-异丙基丙烯酰胺和丙烯酸的线性共聚物P（NIPAM-co-AA）对PNIPAM刷进行可逆吸附。虽然这些共聚物在所研究的整个温度范围内都完全可溶于水，但由疏溶剂相互作用驱动的定量吸附仅在刷的LCST以上进行，并且在冷却时完全可逆。同样，使用NIPAM和N,N-二甲基氨基丙基甲基丙烯酰胺的共聚物P（NIPAM-co-MADAP）研究了PAA刷上由静电相互作用驱动的pH响应吸附。在这种情况下，弱聚阳离子的吸附随着PAA刷的电离而增加，相互作用主要位于pH为7时刷的上部，在pH为9时更深地吸附在刷内。
