Co-aggregation process of poly(ethylene oxide)-b-polybutadiene/poly(acrylic acid) based on evolution of interpolymer hydrogen bonding in solutions

Polymer Complexation by Hydrogen Bonding at the Interface

Polymer complexes can form in the bulk and at interfaces. Polymer complex formation in the bulk has been studied for a long time. The recently developed layer-by-layer assembly technique well realizes polymer complexation at interfaces. The layer-by-layer assembly of polymers based on Coulomb forces or hydrogen bonding is a repeated complexation process conducted at a surface. This paper reviews both single (once only) and repeatable interfacial complexation by hydrogen bonding, the available hydrogen bonding pairs for complexation, the thermodynamics and kinetics of complexation, and construction schemes.

Synthesis of poly(acrylic acid) (PAA) modified Pluronic P123 copolymers for pH-stimulated release of doxorubicin

Pluronic P123 was chain-extended at their terminal groups using atom transfer radical polymerization to form poly(acrylic acid) (PAA) tails and obtain the PAA-b-P123-b-PAA (P123-PAA) copolymer. The incorporation of PAA had the effect of increasing the carrier's drug loading capacity of an anti-cancer drug, Doxorubicin (DOX), and also allowed for pH-controlled release of the drug. Drug release assays showed that up to 60% of DOX cargo could be retained in the DOX/P123-PAA complex for 3 days at normal physiological pH (7.4). This was then followed by a secondary burst release of DOX when the environment became more acidic (pH 5). Therefore, it was possible that the more acidic physiological environment of tumor sites could be used to trigger an accelerated release of DOX from the drug carriers. The material was demonstrated for potential application in the delivery of cationic drugs for cancer treatment.

Hydrogen-bonding-induced complexation of polydimethylsiloxane-graft-poly(ethylene oxide) and poly(acrylic acid)-block-polyacrylonitrile micelles in water

Polydimethylsiloxane-graft-poly(ethylene oxide) (PDMS-g-PEO) copolymers form micelles in water with PDMS as the core and PEO as the corona. The introduction of poly(acrylic acid)-block-polyacrylonitrile (PAA-b-PAN) block copolymers in water leads to the formation of micellar complexes due to the hydrogen bonding between carboxyl groups and ether oxygens among the PAA and PEO chains in the corona of the micelles. The effects of pH, molar ratios (r) of PAA/PEO, and the standing time on the directly mixing these two micelles in water have been investigated using laser light scattering (LLS) and transmission electron microscopy (TEM). Our results showed that the complexation between PAA and PEO in the corona was greatly enhanced at a pH below 3.5. For a fixed pH value, the interactions between these two micelles in water were governed by the value of r. At r < ∼0.6, mixing the two micelles in water resulted in a large floccule because the smaller PAA-b-PAN micelles act as physical cross-links, which are absorbed onto one PDMS-g-PEO micelle and simultaneously bonded to PEO chains on the other micelles, forming bridges and causing flocculation. At ∼0.6 < r < ∼1.2, the mixing led to stable micellar complexes with a layer of PAA-b-PAN micelles absorbed onto the initial PDMS-g-PEO micelles. At r > ∼1.2, the resultant micellar complexes first remained stable, but they precipitated from solution after a long time standing.