Rod particle-like viscoelastic behavior of hydroxypropylmethyl cellulose samples with narrow molar mass distributions dissolved in aqueous solutions.
basic_science · Level V
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- Also identified by DOI 10.1039/d6sm00235h.
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Abstract
The viscoelastic behaviors of aqueous solutions of hydroxypropylmethyl cellulose (HpMC) samples with narrow molar mass distributions were investigated over a wide concentration (<i>c</i>) range. The degree of substitution by methyl groups and the molar substitution number by hydroxypropyl groups of the samples were 1.8 and 0.15. The weight average molar masses (<i>M</i><sub>w</sub>) were 210, 310 and 440 kg mol<sup>-1</sup>, and the molar mass distribution indices were less than 1.3 for each sample. The zero-shear viscosity (<i>η</i><sub>0</sub>), the average relaxation time (<i>τ</i><sub>w</sub>), and the steady state compliance (<i>J</i><sub>e</sub>) determined in the <i>c</i> range for HpMC molecules to fully entangle were determined using the molecular number density (<i>ν</i> = <i>cN</i><sub>A</sub>/<i>M</i><sub>w</sub>, where <i>N</i><sub>A</sub> is the Avogadro constant) and the rod particle length (<i>L</i>) of HpMC molecules. The results were reasonably understood on the basis of entangled rod particle suspension rheology, in which <i>η</i><sub>0</sub> and <i>τ</i><sub>w</sub> are described with <i>L</i><sup>3</sup><i>ν</i> and <i>J</i><sub>e</sub><sup>-1</sup> is described with <i>ν</i>. Consequently, all the obtained viscoelastic data clearly revealed that the HpMC molecules behave as rod-like particles even in a fully entangled concentration range.