Grafting of thermosensitive poly(N-isopropylacrylamide) from wet bacterial cellulose sheets to improve its swelling-drying ability

Rasim Alosmanov,Szczepan Zapotoczny,Karol Wolski

doi:10.1007/s10570-016-1120-x

Rasim Alosmanov, Szczepan Zapotoczny + Show 1 more

Open Access

https://doi.org/10.1007/s10570-016-1120-x

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Journal: Cellulose	Publication Date: Nov 15, 2016
Citations: 39	License type: open-access

Affiliation: Jagiellonian University, Baku State University

Abstract

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) is grafted from wet bacterial cellulose (WBC) sheets using atom transfer radical polymerization (ATRP). WBC is recognized as a highly swollen biocompatible material with broad application potential. However, native WBC undergoes drying relatively fast and its reswelling ability diminishes after losing a substantial amount of water. In this work PNIPAM is grafted from WBC to slow down its drying, especially at elevated temperatures, which is relevant for biomedical applications. As a primary step, initiator molecules, 2-bromoisobutyryl bromide, are attached to WBC through linkers that are covalently bound to the cellulose hydroxyl groups. Grafting of PNIPAM is then realized via surface-initiated ATRP in a water/methanol mixture leading to WBC-g-PNIPAM. The modification steps are followed via FT-IR, XRD, elemental analysis, and atomic force microscopy. It is concluded that PNIPAM contributes to ca. 22% of the dry mass of WBC-g-PNIPAM. The samples are subjected to repeating swelling and drying steps at 25 °C and drying at 40 °C. The obtained results indicate that grafted PNIPAM significantly reduces drying of the modified WBC and enables better reswelling after treatment at 40 °C with respect to native WBC. The reported synthetic method may also be used for grafting other polymers bringing additional functionalities to WBC.

Highlights

Cellulose is the most common, renewable, biodegradable natural polymer resource on earth
We present for the first time the surface modification of wet bacterial cellulose (WBC) sheets by a thermosensitive polymer, poly(N-isopropylacrylamide) (PNIPAM), which was grafted to improve the swelling-drying ability of WBC
The IR spectrum of WBC contains a broad band in the range of 3400–3300 cm-1 that is attributed to the stretching vibrations of the OH groups of cellulose that are involved in the formation of hydrogen bonds and the band around 2900–2800 cm-1 corresponding to C–H stretching (Ullah et al 2016; Amin et al 2012)

Summary

Introduction

Cellulose is the most common, renewable, biodegradable natural polymer resource on earth. Novel demanding biomedical applications have brought more attention to this chemically well-recognized material but in a new structural form called nanocellulose. Nanocellulose is the nanostructured product or extract from the native cellulose found in plants, animals, and bacteria. Three main types of nanocellulose have been identified: cellulose nanocrystals (CNCs), nanofibrillated cellulose (NFC) and bacterial cellulose (BC) (Habibi 2014; Dufresne 2012; Klemm et al 2011). BC demonstrates a series of distinguished structural features and properties such as high purity, a high degree of polymerization, high crystallinity, water content up to 99%, and good mechanical stability. These properties have attracted significant interest from both research scientists and industrialists. BC has wide applications in various fields including: medical, food, advanced acoustic diaphragms, etc. (Klemm et al 2011; Czaja et al 2007)

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