1,720,969 research outputs found
TRANSIENT FLOW BIREFRINGENCE OF CALF SKIN COLLAGEN SOLUTIONS
No full textThe objective of this study is to confirm Doi's molecular theory of the solution of rigid rodlike polymers by analyzing experimentally the transient flow birefringence of collagen solutions. Phase-modulated flow birefringence measurements were performed in the transient flow condition to obtain birefringence and orientation angle of sample simultaneously in a single experimental run. Following the cessation of simple shear flow, relaxation of birefringences was recorded to show two distinct relaxation times due to the molecular weight distribution of calf skin collagen, which turns out to be bimodal. initial rapid drop corresponds to the relaxation of a short chain (monomer) as well as a long chains (dimer), but slow decay follows due to relaxation of long chains only. For a bimodal system consisting of monomer and dimer, such as calf skin collagen. not only the mole fraction hut also the rotational diffusivity can be determined experimentally from thc relaxation of birefringence. Rotational diffusivity decreases rapidly with concentration increase around C=0.94 mg/ml, as expected. But the semidilute regime starts at a rather large value of cL3 owing to the flexibility of polymers chains, which can be resolved by using the effective length proposed by Doi
Determination of Molecular Weight and its Distribution of Polymers by Phase Modulated flow Birefringence
No full text
Determination of molecular weight and its distribution of flexible chain polymer by phase-modulated flow birefringence technique
No full textThe objective of this study is to develop a systematic method to determine molecular weight and its distribution of flexible chain polymer by birefringence experiments. Using the random walk model, birefringence Deltan and orientation angle chi have been optically obtained as functions of molecular weights. To confirm the theory, polystyrene solutions with different molecular weights dissolved in polychlorinated biphenyl were experimented by the phase-modulated flow birefringence (PMFB) method. Birefringence of polystyrene solutions is proportional to (Sigmac(i)M(i)(1.6))gamma(2) and cot(2chi) to (Sigmac(i)M(i)(16)/B(1)Sigmac(i)M(i)(-0.2))gamma. The experimental resets agreed well with the theoretical predictions proposed in this study
QUANTITATIVE-ANALYSIS ON SWELLING BEHAVIOR OF HSMA PVA IPN IONIC GELS UNDER ELECTRIC-FIELD
No full textIn order to explain the electric response of HSMA/PVA IPN ionic gel, polyion concentration (f) and/or interaction parameter (chi(ij)) between gel and water are used, which were previously determined elsewhere by comparing swelling behaviours in the mixed solvents with Tanaka's theory [1]. Ionic polymer gel separated from the electrodes exhibits exponential responses when the electric field is applied or stopped, where the characteristic times for swelling and shrinking and equilibrium swelling ratio are successfully correlated with polyion concentration or interaction parameter. In addition, the strength of field is also an important factor to determine the overall responses. The direction of gel with respect to the electric field is also considered and optimum size was apparent to show maximum swelling
QUANTITATIVE-ANALYSIS ON SWELLING BEHAVIOR OF IONIC GELS IN THE MIXED-SOLVENTS
No full textPhase transition was observed in HSMA/PVA IPN gels having ionizable groups with 3-dimensional network structure in the mixed solvents such as water-methanol, water-acetone or water-ethanol. In order to analyze this phenomena quantitatively, two adjustable parameters related to gel properties were determined from the model based on Tanaka theory. One was the number of dissociated counterions per effective chain (f), the other was the interaction parameters (chi(ij)) between gel and water. As increasing the composition of water, swelling of the gels occurs in the mixed solvent; the gel was shrunk instead when the water content was decreased, which was reversible regardless of the path of swelling and shrinking. A degree of swelling or shrinking of the gel was dependent upon these chi(ij) and f of the gel. With smaller chi(ij) and larger f, more rapid phase transition was observed. Additionally, swelling and shrinking behavior of the gel in system of two solvents and one polymer was influenced not only by chi(ij) between gel and solvents but also by chi(ij) between two solvents
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