Dilute solution properties, chain stiffness, and liquid crystalline properties of cellulose propionate

Abstract

The solution properties of cellulose derivatives are of interest from both technological and purely scientific aspects. At high concentrations these solutions form liquid crystalline structures. In dilute solution cellulosic chains can be described as semiflexible or wormlike with properties intermediate between random coils and rigid rods. A series of fractions of cellulose propionate have been examined by dilute solution viscometry, static and dynamic light scattering, and polarizing microscopy. Power law exponents are considerably larger than those observed for flexible chains and analysis of the intrinsic viscosity and hydrodynamic radii has yielded chain diameters and Kuhn statistical segment lengths. Corresponding aspect ratios from the hydrodynamic measurements are in good agreement with those obtained from polarizing microscopy, as analyzed in light of Flory's theory. Some aggregation and specific solvent effects have been observed, however separation of these effects has proven to be difficult. Results of these studies are compared to previous work for other cellulose derivatives. ©1995 John Wiley & Sons, Inc.

Unraveling the Governing Mechanisms Behind the Chiral Nematic Self-Assembly of Cellulose-Based Polymers

“…M , where M is the molecular weight in g/mol and [η] is the intrinsic viscosity in Pa•s, evaluating the linear slope between these variables, and converting this value into Kuhn length and diameter. 10,11,63,64 Kuhn lengths calculated with the Bohdanecky plot generally agree well with those determined from the Yamakawa−Fujii treatment but the rod diameters obtained with Bohdanecky theory tend to have stronger agreements with experimentally determined values. 11,63 Testing their theory on hydroxypropyl methylcellulose (HPMC), Bustamante, Navarro-Lupioń, and Escalera related the intrinsic viscosity to the solvent's Hansen solubility parameters (δ d,s , δ p,s , and δ h,s ) to estimate the solubility parameters of the polymer (δ d,p , δ p,p , and δ h,p ) through eq 4.…”

“…In the Yamakawa–Fujii model for wormlike chains, the intrinsic viscosity is a function of molecular weight, contour length, Kuhn length, and a constant dependent on the diameter and contour length of the chain . These equations may be applied to simultaneously solve for diameter and Kuhn length through iteration, which tends to underestimate their values. , Alternatively, the chain diameter has been approximated with eq or through X-ray diffraction measurements, such that the Kuhn length remained the only unknown parameter. , Bohdanecky’s technique builds upon the Yamakawa–Fujii method and involves plotting true( M 2 [ η ] true) 1 / 3 vs M , where M is the molecular weight in g/mol and [η] is the intrinsic viscosity in Pa·s, evaluating the linear slope between these variables, and converting this value into Kuhn length and diameter. ,,, Kuhn lengths calculated with the Bohdanecky plot generally agree well with those determined from the Yamakawa−Fujii treatment but the rod diameters obtained with Bohdanecky theory tend to have stronger agreements with experimentally determined values. , …”

A Systematic Coarse-Grained Model for Methylcellulose Polymers: Spontaneous Ring Formation at Elevated Temperature

“…Several computational simulation techniques have been used to study the solvation and gelation behavior of cellulose and its derivatives, including methylcellulose. Unmethylated cellulose oligomers and cellulose melts have also been simulated. − The solvation behavior of multiple cellulosic oligomers in water and organic solvents has been explored, and interactions between cellulosic oligomers and small drug molecules have also been investigated . Even though these atomistic simulations provide important information regarding local chain orientation and intermolecular interaction at the nanometer scale for cellulosic polymers, the time and length scales that could be simulated were too small to reveal the structure and dynamics of gel formation.…”

Analysis of Solvation and Gelation Behavior of Methylcellulose Using Atomistic Molecular Dynamics Simulations

“…Although a considerable amount of experimental effort has been devoted to characterizing both the solvation and the gelation of methylcellulose, computer simulations of cellulosic polymers in water have been rare. To date, cellobiose has been used as a model to study the conformation of cellulose, − while cellulose oligomers of up to nine monomer units in solution have also been simulated. − Simulations up to microsecond scale have been used to study cellulose fibrils and cellulose melts. − However, none of the studies to date have investigated the interaction between multiple cellulosic oligomers in aqueous solution in order to probe the very important yet unsolved gelation mechanism of methylcellulose. Here we present a simulation study probing the solvation behavior of methylcellulose and attempt to understand better the formation of a thermoreversible gel network using atomistic molecular dynamics (MD) simulations.…”