Hydrogen-Bonded Structure of Water in the Loop of Anchored Polyrotaxane Chain Controlled by Anchoring Density.

Keishi Akada,Rina Maeda,Jun Miyawaki,Kosuke Yamazoe,Yoshihisa Harada,Kohzo Ito

doi:10.3389/fchem.2021.743255

Abstract

Hydrogen-bonded network of water surrounding polymers is expected to be one of the most relevant factors affecting biocompatibility, while the specific hydrogen-bonded structure of water responsible for biocompatibility is still under debate. Here we study the hydrogen-bonded structure of water in a loop-shaped poly(ethylene glycol) chain in a polyrotaxane using synchrotron soft X-ray emission spectroscopy. By changing the density of anchoring molecules, hydrogen-bonded structure of water confined in the poly(ethylene glycol) loop was identified. The XES profile of the confined water indicates the absence of the low energy lone-pair peak, probably because the limited space of the polymer loop entropically inhibits the formation of tetrahedrally coordinated water. The volume of the confined water can be changed by the anchoring density, which implies the ability to control the biocompatibility of loop-shaped polymers.

Highlights

Water is well known to play an important role in most biological processes by mediating specific functions, such as biocompatibility of biomaterials (Bag and Valenzuela, 2017; Laage et al, 2017)
Specific hydrogen-bonded structure of incorporated water into polyrotaxane polymer films was investigated by O 1s X-ray emission spectroscopy
By changing the density of anchoring molecules that determine the number of fixing points in the main chain of the polyrotaxane polymer, we controlled the size of the confined space in the large slack of the polymer loop and the amount of absorbed water in it

Summary

Introduction

Water is well known to play an important role in most biological processes by mediating specific functions, such as biocompatibility of biomaterials (Bag and Valenzuela, 2017; Laage et al, 2017). Much debate still exists on the structure of water that provides biocompatibility and how to design biomaterials to improve this function (Jena and Hore, 2010; Tanaka and Mochizuki, 2010; Bag and Valenzuela, 2017; Laage et al, 2017). An excellent anti-fouling property [hereafter referred to as biocompatibility because this is often linked to nonbiofouling (Schlenoff, 2014)] has been reported for looped polymers (Yamada et al, 2012; Kang et al, 2016; Benetti et al, 2017). The higher resistance of the looped chains towards external compression translated into an excellent biocompatibility, a protein repellent behavior (Yamada et al, 2012; Benetti et al, 2017). The looped shape accommodates water molecules inside loops having a size of a few nanometers

Methods

Results

Conclusion