Molar substitution cellulose polymer

Hydroxyethyl cellulose (HEC) is a water-soluble nonionic polymer having the general structure shown in Figure 5.14 [27], The water solubility of HEC depends upon DS and the molar substitution (MS also termed moles of substitution). 

The primary factors governing mesophase formation for cellulose derivatives is not only chain stiffness, but also the type and degree of substitution, the molar mass of the polymer, as well as the solvent and the temperature [103]. Among the water-soluble cellulose biopolymers, HPC is still the most investigated derivative (it forms stable and easy to handle mesophases) and as such will... 

The insoluble cellulose derivatives utilized for permeation control of various species (e.g. oxygen and water vapor transport in coated pharmaceuticals, contact lenses, packaging, or water and solute transport through semi-permeable membranes in reverse osmosis, as well as drug release from reservoir systems) differ considerably in their permeability characteristics according to the type and extent of substitution, as well as their molar mass. However, very few comparative data are available from the literature on the polymers actually used in biological applications. Recently, new results have been published. Thus, Sprockel et al. [142] determined the water vapor transmission through various CA, CAT, CAB and CAPr films at different relative humidities (Table 22). 

The viscosity of a 1 molar solution of this polymer in benzene is reported to be 150 cP. When the polymerization is carried out without hydrogen peroxide, the viscosity of a solution of comparable concentration is only 92 cP. The technique described above may be modified by use of gradual addition of the monomer. Methyl cellulose may be substituted for poly(vinyl alcohol). 

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