Enhanced specific ion effects in ethylene glycol-based thermoresponsive polymer brushes

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:490

Article

Murdoch, Timothy J.¹  Humphreys, Ben A.¹  Willott, Joshua D.¹  Prescott, Stuart W.²  Nelson, Andrew³  Webber, Grant B.¹  Wanless, Erica J.¹ 

[1] Univ Newcastle, Prior Res Ctr Adv Particle Proc & Transport, Callaghan, NSW 2308, Australia

[2] UNSW Sydney, UNSW Australia, Sch Chem Engn, Sydney, NSW 2052, Australia

[3] Australian Nucl Sci & Technol Org, Lucas Heights, NSW 2234, Australia

关键词: Thermoresponsive polymer;    Responsive polymer;    Polymer brush;    Lower critical solution temperature;    Poly oligo(ethylene glycol methacrylate);    Specific ion effect;    Neutron reflectometry;    Atomic force microscopy;   

DOI  :  10.1016/j.jcis.2016.11.044

来源: Elsevier

【 摘 要 】

The thermoresponse of poly(di(ethyleneglycol) methyl ether methacrylate) (PMEO(2)MA) brushes has been investigated in the presence of monovalent anions at either end of the Hofmeister series using ellipsometry, neutron reflectometry (NR) and colloid probe atomic force microscopy (AFM). NR measurements in deuterium oxide showed no evidence of vertical phase separation perpendicular to the grafting substrate with a gradual transition between a block-like, dense structure at 45 degrees C and an extended, dilute conformation at lower temperatures. All three techniques revealed a shift to a more collapsed state for a given temperature in kosmotropic potassium acetate solutions, while more swollen structures were observed in chaotropic potassium thiocyanate solutions. No difference was observed between 250 mM and 500 mM thiocyanate for a 540 angstrom brush studied by ellipsometry, while the lower molecular weight similar to 200 angstrom brushes used for NR and AFM measurements continued to respond with increasing salt concentration. The effect of thiocyanate on the temperature response was greatly enhanced relative to PNIPAM with the shift in temperature response at 250 mM being five times greater than a PNIPAM brush of similar thickness and grafting density. (C) 2016 Elsevier Inc. All rights reserved.

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