The increase in viscosity is caused by strong internal frictionīetween the randomly coiled and swollen macromolecules and the On the other hand, NMP and DMF hollow fiber membranes yields denser structure with better mechanical properties.High molecular weight polymers greatly increase the viscosity of These observations manifest in DMSO membranes being most porous, with highest permeability and molecular weight cut off with poor tensile strength. This reveals that polymer blend-solvent interaction is weak in case of DMSO than DMF or NMP. The higher red shift of (1747 to 1665 cm 21) after complete phase inversion indicates stronger interaction in DMF and NMP, whereas, no shift in stretching in DMSO indicates weak or no interaction. In depth interaction is conducted with help of FT-IR spectra. Cloud point and LCP analysis too reveal DMSO to be the poorest solvent and liquid-liquid demixing is the governing phenomenon for the phase inversion. The analysis yields that D h ½ is negative for both DMF and NMP indicating miscibility, whereas for DMSO it is positive indicating immiscibility. The deviation intrinsic parameter (D h ½ ) is estimated as well as cloud point, linearized cloud point (LCP), and Fourier transform-infrared (FT-IR) analysis have been performed for the blend membranes. A hydrophilic (cellulose acetate phthalate) and a relatively hydrophobic polymer (polyacrylonitrile, critical surface tension 47.0 mJ/m 2) blend in three solvents, viz., n-methylpyrrolidone (NMP), dimethyl formamide (DMF), and dimethylsulfoxide (DMSO), has been selected as an example to understand the polymeric blend-solvent and nonsolvent interactions. The interactions which govern the morphology of blend hollow fiber membranes is explored in detail in the present work. Solvent effects on segmental dynamics and the temperature–frequency superposition of the relaxation data of the three polysaccharides have been discussed as well.
On the basis of the calculated correlation times for segmental motion, the flexibility of the carbohydrate chains decreases from inulin and dextran following the order inulin>dextran>α-(1→3)-d-glucan>β-(1→3)-d-glucan∼amylose, whereas the rate and the amplitude of the internal rotation of the hydroxymethyl groups about the exocyclic C-5–C-6 bonds showed that the restriction of the hydroxymethyl internal rotation decreases from inulin to amylose following the order inulin>α-(1→3)-d-glucan∼β-(1→3)-d-glucan>amylose. Comparison of the dynamics of polysaccharides has been extended to include amylose and inulin studied previously. The internal rotation of the hydroxymethyl groups about the exocyclic C-5–C-6 bonds superimposed on segmental motion has been described as a diffusion process of restricted amplitude. Among these, the time-correlation function developed by Dejean, Laupretre, and Monnerie (DLM) offered the best quantitative description of the segmental motion of the carbohydrate chains.
The relaxation data of the backbone carbons were analyzed quantitatively by using a variety of theoretical unimodal and bimodal time-correlation functions in an attempt to describe the main carbohydrate chain dynamics as a function of linkage position and stereochemistry.
#Determination of intrinsic viscosity of polymers series#
Variable temperature and magnetic field dependent 13C NMR relaxation measurements (T1, T2, and NOE) were carried out on a series of linear homopolysaccharides: α-(1→3)-d-glucan, β-(1→3)-d-glucan in Me2SO-d6, and α-(1→6)-d-glucan in D2O and Me2SO-d6 dilute solutions.
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