Showing papers by "Mohammad Islam published in 2000"
TL;DR: In this article, two different approaches were taken to prevent the hydrophobic association of HASE polymers in aqueous solution: (1) hydrolyze the polymer and (2) use methyl-β-cyclodextrin, which has a hydrophilic outer shell, to shield the hyrophobes from associating.
Abstract: The characterization of hydrophobically modified alkali-soluble emulsions (HASE) using conventional techniques such as gel permeation chromatography or static light scattering is difficult because of the hydrophobic association. Two different approaches were taken to prevent the hydrophobic association of HASE polymers in aqueous solution: (1) hydrolyze the polymer to dislodge the hydrophobic constituents, and (2) use methyl-β-cyclodextrin, which has a hydrophobic cavity and a hydrophilic outer shell, to shield the hydrophobes from associating. Using these two approaches, the molecular weight (Mw), hydrodynamic radius (Rh), and radius of gyration (Rg) of single chains of these polymers were determined using gel permeation chromatography (GPC) and dynamic (DLS) and static (SLS) light scattering techniques. The molecular weight of the control polymer (i.e., polymers with similar composition but with no hydrophobe) is found to be ∼7.0 × 105 g/mol. The molecular weights of these polymers with C8, C16, and C2...
76 citations
TL;DR: In this article, the authors investigated the inclusion complexation kinetics of methyl-β-cyclodextrin to hydrophobic molecules confined in an isolated droplet with optical tweezers.
Abstract: Inclusion complexation kinetics of methyl-β-cyclodextrin (m-β-CD) to hydrophobic molecules confined in an isolated droplet was investigated with optical tweezers. The radius of the droplet shrank over time as m-β-CD was introduced into the sample chamber due to complexation between the hydrophobic molecules and the m-β-CD molecules. The short time behavior of the droplet shrinkage can be described by a model based on Brownian kinetics. The probability of complexation was greater for a branched 2-hexadecanol than for hexadecane. The probability decreased with increasing chain length for short alkanes. The long time behavior of the droplet shrinkage is surprising because the droplets stopped shrinking even when the uncomplexed m-β-CD concentration was still high. We speculate that surface activities of m-β-CD might have slowed the reaction.
6 citations