From well‐defined diblock copolymers prepared by a versatile atom transfer radical polymerization method to supramolecular assemblies

Abstract

The synthesis of well-defined diblock copolymers by atom transfer radical polymerization (ATRP) was explored in detail for the development of new colloidal carriers. The ATRP technique allowed the preparation of diblock copolymers of poly-(ethylene glycol) (PEG) (number-average molecular weight: 2000) and ionic or nonionizable hydrophobic segments. Using monofunctionalized PEG macroinitiator, ionizable and hydrophobic monomers were polymerized to obtain the diblock copolymers. This polymerization method provided good control over molecular weights and molecular weight distributions, with monomer conversions as high as 98%. Moreover, the copolymerization of hydrophobic and ionizable monomers using the PEG macroinitiator made it possible to modulate the physicochemical properties of the resulting polymers in solution. Depending on the length and nature of the hydrophobic segment, the nonionic copolymers could self-assemble in water into nanoparticles or polymeric micelles. For example, the copolymers having a short hydrophobic block (5 Ͻ degree of polymerization Ͻ 9) formed polymeric micelles in aqueous solution, with an apparent critical association concentration between 2 and 20 mg/L. The interchain association of PEG-based polymethacrylic acid derivatives was found to be pH-dependent and occurred at low pH. The amphiphilic and nonionic copolymers could be suitable for the solubilization and delivery of water-insoluble drugs, whereas the ionic diblock copolymers offer promising characteristics for the delivery of electrostatically charged compounds (e.g., DNA) through the formation of polyion complex micelles. Thus, ATRP represents a promising technique for the design of new multiblock copolymers in drug delivery.

Cellular uptake and cytotoxicity of octahedral rhenium cluster complexes

“…In order to improve water solubility and cell permeation capacity, an amphiphilic diblock copolymer was conjugated to rhenium cluster 1 by esterification reaction in methanolic aqueous solution. As well documented, amphiphilic block copolymers with core-shell architecture could result in improved solubility of poorly water soluble drugs and enhanced thermodynamic stability under physiological condition [25], which might be, therefore, applicable for gene or drug delivery [26]. Our amphiphilic diblock copolymer was prepared by PEGylation of a very hydrophobic hexapeptide ethyl ester, GlyPheLeuGlyPheLeuEt, following the literature procedure [24].…”

Delivery of Nucleic Acids through the Controlled Disassembly of Multifunctional Nanocomplexes

“…Synthesis of PEG 115 -b-(PrMA-co-MAA) and Fab(-S-S-PEG 145 -b-(PrMA 27 -co-MAA 53 ): PEG macroinitiator, i.e., a-(2-bromoisobutyrylate bromide)-v-methyl PEG, was synthesized using methoxy-PEG (M n ¼ 5000) and 2-bromoisobutyryl bromide [36]. The polymerization reactions were carried out by atom transfer radical polymerization (ATRP) of PrMA and tert-butyl methacrylate (tBMA) as reported previously [37].…”

Synthesis and characterization of the PEG‐based nonionic surfactants endowed with carboxylic acid moiety at the hydrophobic terminal

“…A similar bimodal profile of size distribution has been reported for PEG-based copolymes. 29,30 Yamazaki et al also reported the hydrodynamic diameter of 6.0 nm for PEG monododecyl ether, C 12 EO 25 . 31 Taking the reports into consideration, small and large diameters of about 6 and 43 nm might be attributed to a surfactant micelle and a secondary aggregation, respectively.…”