Comparison of the Aggregation Behavior of Di- and Triblock Nonionic Amphiphiles with Linear and Cyclic Hydrophobic Tails

Abstract

The micellization characteristics of nonionic surfactants of the type C7E26 and symmetric C7E26C7 where C7 = the heptanoic acid (C7H14O2) or the cyclohexanecarboxylic acid (C7H12O2) group is investigated. Structural formulas being nearly the same, the linear and cyclic analogues possess roughly the same molecular weights and hydrophilic−lipophilic balance (HLB) values. Surface tension and fluorescence experiments provide information on the thermodynamics of micellization, interfacial adsorption, mean aggregation number, etc. Comparisons are made between linear and cyclic analogues and between diblocks and triblocks. The results indicate that, compared to their linear counterparts, amphiphiles with cyclic hydrophobes possess higher CMC values and the micelles formed are less compact with lower aggregation number. A qualitatively similar trend is seen between diblock and triblock surfactants. The results for triblocks are consistent with a micellar structure in which the PEG chain folds to insert both the terminal hydrophobic segments into the micellar core.

New biomaterials from renewable resources – amphiphilic block copolymers from δ-decalactone

“…Micelle-like nanoparticles of mPEG-b-PDL and mPEG-b-PCL micelles formed by nanoprecipitation routes were of similar sizes (∼40 nm), whereas the sizes of ABA (PDL-b-PEG-b-PDL) and ABC (mPEG-b-PDL-b-PPDL) tri-block copolymers were considerably larger (85-165 nm). The bimodal size distributions observed with the empty ABA type copolymer (PDL-b-PEG-b-PDL) micelles were probably due to additional hydrophobic-hydrophobic inter-actions between micelle cores, which led to aggregation and clustering 40 This mechanism is in accord with proposals that ABA type block copolymers can assemble in flower-shaped micelles 41 leading to a decrease in PEG chain length at the periphery separating the core from the surrounding aqueous environment. In addition, the PDL-b-PEG-b-PDL copolymer was synthesised using a shorter chain PEG (M n = 4.0 kDa) compared to the di-block (mPEG-b-PCL and mPEG-b-PDL) co-polymers and hence was expected to have a less dense hydrophilic corona.…”

Characterization of pegylated copolymeric micelles and in vivo pharmacokinetics and biodistribution studies

“…Theoretically, amphiphilic triblock copolymers enabled to form self‐assemble micelles as soon as the concentration increased above the CMC, where the hydrophilic PEG chain was folded back and inserted the hydrophobic chains inside the core of micelles 16, 17. The ability to form core‐shell structures by our amphiphilic copolymers was further evaluated by using 1 H‐NMR technique.…”

Solubilization and Stabilization of Membrane Proteins by Cycloalkane-Modified Amphiphilic Polymers

“…The improvement of solubilization achieved with CyclAPols is therefore due to the cyclic nature of the hydrophobic side groups. In the case of detergents, the few available data suggest that cyclic hydrophobic groups markedly affect their solution behavior. − In-tail cycles restrict packing possibilities, which is reflected in a lower propensity to self-assemble (up to 8 times higher critical micelle concentration than linear counterparts, a lower aggregation number, and a more hydrated core). − A lower stability of intrapolymer hydrophobic association in CyclAPols likely makes these groups more available to interact with lipid bilayers and thus to extract MPs. However, other molecular parameters may also play a role.…”