Phase processes and energetics of spontaneous change in the dimensions of acetate fibers in nitromethane vapors

Spontaneous elongation of acetate fibres in dimethyl sulfoxide vapors: dynamics, structure, energetics

“…This does not take place in hydrothermal elongation of cellulose acetates in water-phenol medium [1,2]. Directed optical anisotropy stable in time [4] that does not obey Fick's law, anomalous sorption [7,8], variation of the sign of the specific optical rotation within wide limits [4,5], the capacity of the cholesteric coil, for example, to pass from the rotating polarization plane to the right into levorotatory and vice versa [4,5,8], etc.Since spontaneous elongation of cellulose acetates occurred in solvent vapors and not in liquid medium (where both swelling and partial dissolution could have occurred), we found methods for a multistage study of the reaction of the polymer with the solvent and controlling the process. This also allowed solving practical problems [7,9,[13][14][15].…”

“…It was found that the stereomeric structure of the polysaccharide changes during a cyclic change in the size of the fibre, confirmed by inversion of the specific optical rotation sign. The data obtained can be described in terms of phase and conformational transitions and the mechanism of reaction of the polymer with the solvent vapors forming the LC phase with it.The spontaneous elongation of acetate fibres and films under the effect of active media -an aqueous solution of phenol and nitromethane vapors -noted in [1][2][3][4][5] is considered one of the clearest visually observable effects of spontaneous orientation ordering of macrochains [6].Of these two systems, the acetate fibre-nitromethane vapors system has been investigated from different points of view [3][4][5][7][8][9]. Nitromethane is a mesophasogenic solvent in which cellulose acetates form a lyotropic liquid-crystalline (LC) phase [4,8,[10][11][12].…”

“…The spontaneous elongation of acetate fibres and films under the effect of active media -an aqueous solution of phenol and nitromethane vapors -noted in [1][2][3][4][5] is considered one of the clearest visually observable effects of spontaneous orientation ordering of macrochains [6].…”

“…Nitromethane is a mesophasogenic solvent in which cellulose acetates form a lyotropic liquid-crystalline (LC) phase [4,8,[10][11][12]. The specific reaction of the polymer with the solvent is followed in many new events and characteristics [3][4][5][7][8][9]. This is primarily the kinetic "reversibility" of the spontaneous change in the linear dimensions of an anisodiametric sample: after self-elongation in the same conditions, i.e., in nitromethane vapors, the elongated fibre returns to the initial linear dimensions [3,5].…”

“…The specific reaction of the polymer with the solvent is followed in many new events and characteristics [3][4][5][7][8][9]. This is primarily the kinetic "reversibility" of the spontaneous change in the linear dimensions of an anisodiametric sample: after self-elongation in the same conditions, i.e., in nitromethane vapors, the elongated fibre returns to the initial linear dimensions [3,5]. This does not take place in hydrothermal elongation of cellulose acetates in water-phenol medium [1,2].…”