Synthesis of biodegradable amphiphilic thermo‐responsive multiblock polycarbonate and its self‐aggregation behavior in aqueous solution

Abstract

Amphiphilic thermo-responsive multiblock polycarbonates consisting of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) were facilely synthesized using triphosgene as coupling agent. The structures and molecular characteristics of the polycarbonates were confirmed by 1 H-NMR, FT-IR and Gel permeation chromatography (GPC). The crystallization behavior and thermal properties of the polycarbonates were studied using X-ray diffraction (XRD), Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Surface tension measurements confirmed that the critical micelles concentration of polymeric micelles were concentration ranges, which varied from about 2-70 mg/L to 5-40 mg/L with increasing PEO/PPO composition ratio from 0.8 to 1. Dynamic light scattering (DLS) experiments showed bimodal size distributions, the aggregates size increased with increasing the concentration of the polycarbonates aqueous solutions. The size of the aggregates acquired from TEM was smaller than that from DLS owing to the fact that TEM gave size of the aggregates in dry state rather than the hydrodynamic diameter. The degradation process revealed that the degradation rate of the aggregates could be accelerated with an increase in temperature. Moreover, the more the polycarbonate was hydrophilic, the faster was its degradation. Rheological measurements suggested that these multiblock polycarbonates were thermo-responsive and by regulating the PEO/PPO composition ratio they could form a gel at 37 C.

PAA-g-PPO Amphiphilic Graft Copolymer: Synthesis and Diverse Micellar Morphologies

“…As for PPO-based amphiphilic copolymers, only a few examples touched on their self-assembly properties in the selective solvents. Liu and co-workers reported the reversible temperature-induced self-assembly process of PPO-based block copolymers. , Furthermore, the sizes and morphologies of PEO- b -PPO amphiphilic diblock copolymer changed as the variation of the concentration of the aqueous solution . However, none has reported the micellar morphology of PPO-based amphiphilic graft copolymer.…”

“…Moreover, PPO homopolymer prepared by anionic polymerization contains one or two hydroxyl end functionalities, and this kind of commercially available functional PPO homopolymer is in favor of almost unlimited chemical modification. PPO-based block copolymers (PEO was usually selected as another block) − have been extensively studied due to their convenient syntheses, and only a few examples touched on PPO-based graft copolymers. − Most of these graft copolymers were synthesized from PPO-based macromonomers containing (meth)acrylate end groups using living or traditional radical polymerization, and ester linkages were employed to connect PPO side chains with the hydrophobic backbone in these “graft” copolymers, implying PPO segments would be detached after the hydrolysis of ester connections. − PPO-based graft copolymers can also be obtained via other types of PPO-based macromonomers by the condensation polymerization or catalyzed coupling polymerization. , Moreover, nucleophilic substitution reactions , were also applied to synthesize the graft copolymers containing PPO side chains, whose backbone and side chains were prepared independently; however, the grafting densities of these graft copolymers were not clear or very low (60/1230 = 4.88%), and they possessed broad molecular weight distributions, , this indicating that these graft copolymers might not be well-defined. The pendant hydroxyls of ethylene−vinyl alcohol copolymer were also employed to initiate anionic graft polymerization of propylene oxide to afford the densely grafted polymers containing PPO side chains .…”

Physical Characterisation and Long-Term Stability Studies on Quaternary Ammonium Palmitoyl Glycol Chitosan (GCPQ)—A New Drug Delivery Polymer

“…). Block copolymer micellar dispersions exhibit viscoelastic properties in a concentration, temperature, and polymer hydrophobicity dependent manner and are believed to form transient networks in which micelles are linked via entangled polymer chains. We have been unable to find examples of comb type polymers, such as GCPQ, comprising a water soluble backbone and hydrophobic pendant groups, forming transient micellar networks without the addition of co‐surfactants.…”

Topical delivery of ocular therapeutics: carrier systems and physical methods

“…[54,55,83,180] Currently, different polymers are blended to improve the gel characteristics for topical ocular delivery systems. [78,82,178] Poloxamers, for example, have been widely studied as thermosensitive in-situ-forming gels, [84,86,181] but they suffer the major drawback of having weak mechanical strength. [182] To solve this problem, poloxamers have been blended with polyacrylic acid, [183] alginate [85] and chitosan.…”