Synthesis and morphology transformation of amphiphilic diblock polyurethane copolymers in aqueous solution

Abstract

Amphiphilic block copolymers possess both hydrophobic and hydrophilic properties and can form versatile micellar structures in aqueous solution. The aim of the research presented was to prepare a series of non‐ionic amphiphilic diblock polyurethane copolymers (PUn) based on isophorone diisocyanate, monoallyl‐end‐capped poly(ethylene oxide) and poly(propylene oxide) (PPO), followed by an investigation of their micellization properties and morphology transformation in aqueous solution. The PUn samples were synthesized by condensation polymerization. These polyurethanes exhibit surface tension as low as 33.7–37.0 mN m−1. There is an obvious decrease in critical micelle concentration as the hydrophobic PPO molecular weight increases. According to transmission electron microscopy, the morphology of aggregates of the copolymers can be tuned by varying the concentration in aqueous solution rather than organic solvent. For example, for PU7, large compound micelles are produced instead of vesicles. For PU17, the concentration can be used to control the size and thickness of vesicles. Vesicle size increases from 60 to 500 nm and vesicle thickness from 40 to 60 nm with concentration ranging from 0.003 to 0.03 wt%. The study shows that the copolymers in aqueous solution have excellent surface activities. In addition, they can self‐assemble into large compound micelles or vesicles at certain concentrations. Moreover, the synthesis method described allows one to obtain a desired morphology of aggregates by adjusting the composition of hydrophilic and hydrophobic segments, which provides a novel and simple way to obtain particles on the nanometer scale. Copyright © 2010 Society of Chemical Industry

Acrylamide‐b‐N‐isopropylacrylamide block copolymers: Synthesis by atomic transfer radical polymerization in water and the effect of the hydrophilic–hydrophobic ratio on the solution properties

“…This is expected as the larger the PNIPAM blocks are, the larger the effect of its lower hydrophilicity . The order of magnitudes 10 −6 and 10 −7 M coincide with that given in literature for amphiphilic block copolymers . The formation of micelles is a result of the concentration of polymer being high enough that interaction between the PNIPAM blocks is beneficial.…”

“…The formation of micelles is a result of the concentration of polymer being high enough that interaction between the PNIPAM blocks is beneficial. The aggregation of less hydrophilic blocks result in the formation of a micelle with a hydrophobic core (PNIPAM) and a hydrophilic corona (PAM) keeping the micelles stable in the water solution …”

“…This confirms the general trend for nonionic surfactants where the CMC increases as the hydrophilic content increases. In literature, however, the hydrophilic/hydrophobic balances are depicted by the HLB number and not the solubility parameter . The result of each gives the same structure property relationship indicated in Figure , only the method of calculation differs.…”

Polymeric Surfactants: Synthesis, Properties, and Links to Applications

“…In this respect the dependence of the aggregate structures on temperature, 413 shear field, 420 and salt concentration 70,390,421 have been reported already and extensively studied. The kind of aggregate can be molecularly controlled, in the case of block copolymers, by a correct design of the blocks' chemical structure, 102,236,390,422 length, 91,92,229,423 and topology. 88,424 In this respect an absolute ranking of these two factors, and even less a general quantification of both, is still lacking in the open literature.…”

Self-assembly of biodegradable polyurethanes for controlled delivery applications

“…Several reports have dealt with the self-assembly behavior of nondegradable polyurethane copolymers with or without charged groups based on isophorone diisocyanate (IPDI), PEG and poly(propylene oxide) (PPO). [90][91][92][93] These polymers possess excellent surface activities in water, and can self-assemble into stable micelles, large compound micelles or vesicles, the morphology of which could be tuned by varying the polymer concentrations. 91,92 Since the biodegradability and biocompatibility of biomaterials are of crucial importance for clinical applications, currently, research interests have been mainly focused on the development of self-assembled biodegradable SPUs as micellar drug delivery vehicles for cancer therapy.…”