Characterization of Interactions in Aqueous Solutions of Hydroxyethylcellulose and Its Hydrophobically Modified Analogue in the Presence of a Cyclodextrin Derivative

Abstract

The formation of associative networks in semidilute aqueous solutions of hydrophobically modified hydroxyethylcellulose (HM-HEC) is dependent on intermolecular hydrophobic interactions. Addition of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) monomers to the system provides decoupling of these associations via inclusion complex formation with the polymer hydrophobic tails. Results from viscosity, polymer NMR self-diffusion, and dynamic light scattering (DLS) measurements show that the hydrophobic interactions in HM-HEC solutions are effectively suppressed when the level of HP-beta-CD addition increases. Small-angle neutron scattering (SANS) results reveal that the large-scale association complexes in HM-HEC solutions are strongly diminished when the concentration of HP-beta-CD rises. The time correlation data obtained from the DLS experiments unveiled the existence of two relaxation modes: one single exponential at short times followed by a stretched exponential at longer times. The fast mode is always diffusive, whereas the slow mode exhibits progressively stronger wavevector dependence as the intensity of the hydrophobic interactions increases. This feature, as well as the accompanying drop of the stretched exponential beta as the HP-beta-CD concentration decreases, is attributed to enhanced hydrophobic interactions and can be well rationalized in the framework of the coupling model of Ngai.

Adsorption of cellulose derivatives on flat gold surfaces and on spherical gold particles

“…A-0382) acquired from Hercules, Aqualon Division, was used as the hydrophilic polymer and served as the precursor for the synthesis of the hydrophobically modified analogue (HM-HEC). The degree of substitution of hydroxyethyl groups per repeating anhydroglucose unit for HEC was 2.5 (given by the manufacturer), and the weight-average molecular weight was determined to be M w = 400,000 by intensity light scattering [31].…”

“…The hydrophobically modified analogue was synthesized according to a standard procedure [32], and the fine points of the synthesis as well as the details of the characterization of this sample have been reported previously [31]. The chemical structure and purity of the HM-HEC were ascertained by 1 H NMR and the degree of hydrophobic modification (glycidyl hexadecyl ether groups, n-C 16 H 33 ) was determined from the peak ratios between the anisomeric protons and the methyl protons of the glycidyl hexadecyl chain (see reference [31]).…”

Use of cellulose derivatives on gold surfaces for reduced nonspecific adsorption of immunoglobulin G

“…The degree of substitution of hydroxyethyl groups per repeating anhydroglucose unit for HEC is 2.5 (given by the manufacturer). The weight-average molecular weight (M w = 400,000) of this sample in dilute aqueous solution was determined by intensity light scattering at 25 • C [13]. The HM-HEC sample was synthesized according to a procedure described elsewhere [14], and the details of the synthesis as well as the characterization of this sample have been reported previously [13].…”

“…The weight-average molecular weight (M w = 400,000) of this sample in dilute aqueous solution was determined by intensity light scattering at 25 • C [13]. The HM-HEC sample was synthesized according to a procedure described elsewhere [14], and the details of the synthesis as well as the characterization of this sample have been reported previously [13]. The chemical structure and purity of the HM-HEC were ascertained by 1 H NMR and the degree of hydrophobic modification (glycidyl hexadecyl ether groups, n-C 16 H 33 ) was determined from the peak ratios between the anisomeric protons and the methyl protons of the glycidyl hexadecyl chain [13].…”

Synthesis and solution behavior of poly(ɛ-caprolactone) grafted hydroxyethyl cellulose copolymers

“…Hydrophobically modified cellulose derivates have been investigated extensively [11][12][13][14][15][16][17][18][19][20]. Even the substitution degree of (HMDS) (AR), trimethylsilyl chloride (TMCS) (AR), stannous octoate [Sn(Oct) 2 ], dimethylformamide (DMF) and other reagents were purchased from National Drug Co. Ltd. (Shanghai) and used without purification.…”