Structure of Hydrogels Based on Lyotropic Phases of Cellulose Derivative as Studied by Raman Spectroscopy

✍ Scribed by Aleksandra Joachimiak; Tomasz Halamus; Piotr Wojciechowski; Jacek Ulanski

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 157 KB
• Volume: 206
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200400132

✦ Synopsis

Abstract

Summary: Photopolymerisation of acrylic acid (AA) to poly(acrylic acid) (polyAA) in the lyotropic liquid crystalline (LLC) phase of hydroxypropylcellulose (HPC) in the AA‐water mixture, as well as the influence of mesomorphic organisation of the HPC on the structure of water was studied. Raman and thermo‐optical analysis results reveal that the lyotropic phase of the HPC/AA‐H~2~O can be used as a template system suitable for the formation of anisotropic hydrogels. The mesomorphic organisation of the HPC/AA‐H~2~O phase is preserved after photopolymerisation induced by UV radiation. Also the structure of water, strongly disturbed in the LLC‐phase as compared with the structure of liquid water, is preserved after the photopolymerisation. Apart from the water originating from the LLC‐phase of HPC/AA‐H~2~O, the anisotropic hydrogel may also contain water molecules taken up during immersion of the hydrogel in liquid water. Raman spectroscopy reveals that the water resulting from the swelling has a structure close to that of liquid water. Because the anisotropic hydrogel network is created by hydrogen bonds between HPC, water and polyAA, it is not stable when immersed in water for long time. An increased stability of the LC‐organisation of the hydrogel network can be achieved by crosslinking of the hydrogel with calcium ions, which can form a salt with polyAA, as confirmed by Raman spectroscopy.

Comparison of the (a) Raman spectrum of liquid water with (b) that of water in the hydrogel, illustrating the influence of the mesomorphic organization in the hydrogel on the water structure.

magnified imageComparison of the (a) Raman spectrum of liquid water with (b) that of water in the hydrogel, illustrating the influence of the mesomorphic organization in the hydrogel on the water structure.