Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (9): 2318-2326.doi: 10.3866/PKU.WHXB201605181

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Surface Patterning and Force-Induced Reversible Structural Transformation of a PVP-Chol Supramolecular Polymer Brush

Shan-Shan LIU,Shan JI,Qi-Bin CHEN*(),Chang-Jun PENG,Hong-Lai LIU   

  • Received:2016-04-11 Published:2016-09-08
  • Contact: Qi-Bin CHEN E-mail:qibinchen@ecust.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21273074);the National Natural Science Foundation of China(21576079);the National Natural Science Foundation of China(91334203);the National Natural Science Foundation of China(21476070);the 111 Project of Ministry of Education of China(B08021)

Abstract:

A supramolecular polymer brush composed of polyvinylpyrrolidone-cholesterol (PVP-Chol) was fabricated based on intermolecular hydrogen bonding between the ketone groups of the PVP moieties and the hydroxyl groups of the cholesterol, both in solution and at the air/water interface. These confirmations were confirmed by Fourier transform infrared (FT-IR) spectroscopy, surface pressure versus molecular area (π-A) isotherms, and atomic force microscopy (AFM). At surface pressures up to 2.5 m N·m-1, the interfacial film was composed of cholesterol-enriched regions and PVP-Chol nanofibril domains. Interestingly, oversurface pressures, the structure of the PVP-Chol-enriched domains evolved frominitial irregular shapes, to crescent and heart-shaped zones, and then to circular shapes. This transition indicated the controllability of such domains during compression of a complex monolayer at relatively low surface pressures. Above 2.5 m N·m-1, the circular PVP-Chol domains disappeared and fibrous aggregates were formed at the air/water interface. The height of the comb-like PVP-Chol nanofibrils could be reversibly varied between approximately 4.3 and 1.8 nm by adjusting the voltage applied to piezoceramics during the AFM scanning process. These results demonstrate that the reversible structural transformation of the PVP-Chol complex from cylindrical to elliptic cylindrical is induced by the applied force of the AFM tip up to a value of 1.0 m N·m-1. These data provide important and useful information that improves our understanding of the relationship between the structures and performances of supramolecular polymer brushes, and should extend the range of applications of cholesterol-functionalized polymers fabricated via a simple mixing strategy.

Key words: Hydrogen bonding, Air/water interface, Domain, Nanofibril, Structural evolution, Tip-sample force

MSC2000: 

  • O647