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γ‐Ray polymerization of lyotropic solutions of cellulose derivatives under retention of the macroscopic order
Author(s) -
Hohn Wilfried,
Tieke Bernd
Publication year - 1997
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1997.021980303
Subject(s) - lyotropic , polymerization , materials science , polymer chemistry , polymer , cellulose , birefringence , chemical engineering , acrylate , dispersity , irradiation , phase (matter) , degree of polymerization , hydroxypropyl cellulose , chemistry , composite material , organic chemistry , optics , monomer , liquid crystalline , physics , nuclear physics , engineering
Two new lyotropic solutions of cellulose derivatives are reported which can be polymerized upon γ‐irradiation. The first solution consists of hydroxypropylcellulose (HPC) in N , N ‐dimethylacrylamide (DMAcr) and the second of 2‐(acryloyloxy)propylcellulose (APC; degree of substitution (DS) = 0.18) in water. Both solutions were characterized using refractive index measurements, polarizing microscopy and diffuse reflection spectroscopy. For solutions of HPC in DMAcr, it was demonstrated that they exhibit anisotropic phase behaviour at concentrations higher than 45 wt.‐% within a limited temperature range. Highly concentrated solutions of about 70 wt.‐% also showed cholesteric phase behaviour with iridescent colours. Upon γ‐irradiation, the solvent DMAcr rapidly polymerized. A conversion to 90% of polymer was reached at a dose of 5 kGy. Molecular composites of HPC in polymerized DMAcr were obtained in which the macroscopic order was preserved. Shear‐deformed samples were still birefringent and exhibited band textures, when viewed between crossed polarizers, and light reflection of the cholesteric samples still occurred at the same wavelength as before irradiation. The polymerized samples showed an extended temperature stability, the anisotropy being stable up to approximately 150°C. The second solution of APC in water also exhibits cholesteric phase behaviour at a concentration of 61.5 wt.‐%. Upon γ‐irradiation, the polymer chains undergo rapid cross‐linking via the reactive acrylate groups and form a network in which the cholesteric order is preserved. The cross‐linked APC films are swellable in water and retain their anisotropic order when the concentration of the solution is varied between 40 and 100 wt.‐% of APC. The materials properties of the two systems after polymerization are compared.