Hydrophilic block copolymers

Qi, L. Colfen, H. and Antonietti, M. (2001). Synthesis and Characterization of CdS Nanoparticles Stabilised by Double Hydrophilic Block Copolymers. Nano Lett, 1, 61-65. 

Vaterite is thermodynamically most unstable in the three crystal structures. Vaterite, however, is expected to be used in various purposes, because it has some features such as high specific surface area, high solubility, high dispersion, and small specific gravity compared with the other two crystal systems. Spherical vaterite crystals have already been reported in the presence of divalent cations [33], a surfactant [bis(2-ethylhexyl)sodium sulfate (AOT)] [32], poly(styrene-sulfonate) [34], poly(vinylalcohol) [13], and double-hydrophilic block copolymers [31]. The control of the particle size of spherical vaterite should be important for application as pigments, fillers and dentifrice. 

These double hydrophilic block copolymers exhibit stimuli-responsive properties and have potential biotech applications. 

Colfen, H. (2001) Double-hydrophilic block copolymers synthesis and application as novel surfactants and crystal growth modifiers. Macromotecular Rapid Communications, 22, 219-252. 

Double-Hydrophilic Block Copolymers in Aqueous Solution. 94... 

Selected examples of block copolymer micelles in both aqueous and organic media will then be presented in Sects. 3 and 4. Section 4.3 emphasizes stimulus-responsive micellar systems from double-hydrophilic block copolymers. Prediction of the dimensional characteristic features of block copolymer micelles and how it varies with the composition of the copolymers will be shortly outlined in Sect. 5, with a consideration of both the theoretical and experimental approaches. Tuning of micellar morphology and triggering transitions between different morphologies will then be discussed in Sect. 6. 

AB block copolymers containing two water-soluble blocks are often referred to as double-hydrophilic block copolymers. These copolymers have spurred much interest in recent years because they can generally be transformed into amphiphilic copolymers once an adequate stimulus is applied. In other words, one of the hydrophilic water-soluble blocks can be transformed into a hydrophobic block whenever a given property of the aqueous medium is changed. Since these copolymers may contain one or two polyelectrolytic blocks, the typical features of polyelectrolytes described in Sect. 4.2 should also be considered for some double-hydrophilic block copolymers. 

Thermosensitive double-hydrophilic block copolymers micelles have been reported essentially for systems containing blocks exhibiting a LOST in water such as PMVE [189] or PNIPAM. These blocks have been generally associated to PEO blocks. At temperatures below the LOST, both blocks are soluble and... 

Stimulus-reponsive micelles have been intensively investigated during the last 5 years, and further developments could be expected. These micellar systems have been essentially prepared from double-hydrophilic block copolymers and from micelles with noncovalent complexes in the core. The interest related to these micellar systems stems from their potential applications, as briefly discussed in Sect. 4.3. 

ATRP is a powerful synthetic tool for the synthesis of low molecular weight (Dp < 100-200), controlled-structure hydrophilic block copolymers. Compared to other living radical polymerisation chemistries such as RAFT, ATRP offers two advantages (1) facile synthesis of a range of well-defined macro-initiators for the preparation of novel diblock copolymers (2) much more rapid polymerisations under mild conditions in the presence of water. In many cases these new copolymers have tuneable surface activity (i.e. they are stimuli-responsive) and exhibit reversible micellisation behaviour. Unique materials such as new schizo-... 

Citrate-capped Au NPs have been coated with a layer composed of the double hydrophilic block copolymer polyethylene oxide)-block-poly(2-(dimethylamino)eth-yl methacrylate)-SH (PEO-b-PDMA-SH) leading to core-shell, almost spherical, Au NPs of about 18 nm. The shell cross-linking of these hybrid Au NPs gives rise to high colloidal stability [122]. 

Polyelectrolyte complexes of retinoic acid have been well investigated, they are pharmaceutically active surfactants. In the following, we will therefore discuss the physicochemical properties of drug carriers formed by synthetic polyamino acids, polyethyleneimine, double hydrophilic block copolymers and retinoic acid. 

Very recently, these processes were extended for the generation of helical morphologies of K2SO4 crystals [38] generated in the presence of polyacrylic acid, Fig. la,b, and for the preparation of helices from the achiral BaC03 nanocrystals [39,40] grown in the presence of racemic hydrophilic block copolymers. 

Antonietti M, Breulmann M, Goltner CG, Colfen H, Wong KKW, Walsh D, Mann S (1998) Inorganic/organic mesostructures with complex architectures precipitation of calcium phosphate in the presence of double-hydrophilic block copolymers. Chem Eur J 4(12) 2493-2500... 

Recent attempts to prepare 26 by RAFT, however, failed [153]. Double hydrophilic block copolymers of NIPAM and 23e [154], as well as of N,N-diethylacrylamide and 23b [155], were prepared with the CTA benzyl dithiobenzoate, and exhibit LCST and UCST behavior in water. The new polymer 51 is also part of amphiphiUc di- and triblock copolymers [152]. Diblock copolymers with poly(ethylene glycol) methyl ether acrylate, dimethylacry-lamide, or 4-vinylstyrene sulfonate are macrosurfactants with a switch-able hydrophobic block. Triblock copolymers containing additionally 4-vinylbenzoic acid differ in the nature of the hydrophilic part [152]. Near-monodisperse block copolymers of N,N-dimethacrylamide and 49a were synthesized in different ways via macro-CTAs of both monomers as the first step. Such sulfobetaine block polymers form aggregates in pure water but are molecularly dissolved after addition of salt [152,156,157]. 

Amphiphilic block copolymers containing a cationic block may carry as the second block a hydrophilic or a hydrophobic one. Those containing a hydrophilic second block belong to the so called double-hydrophilic block copolymers (DHBC), which have recently been reviewed [60]. This promising class of polymers has potential applications in drug-carrier systems, gene therapy, desalination membranes, as switchable amphiphiles, and others [45, 60, 77]. 

Scheme 11 A novel route to double hydrophilic block copolymers...

Poly(propylene fumarate-co-ethylene glycol) (PF-co-EG) is a hydrophilic block copolymer that can be cross-linked chemically or by UV light. When used as an injectable cell scaffold in bone and vascular tissue engineering, this block copolymer degrades through the ester bonds in the PF blocks. ... 

The preparation methods for mesoporous support materials can be classified by the nature of the (endo-) template, which can either be ionic (e.g. alkyl trimethylammonium halides leading to MCM materials i or neutral (e.g. hydrophilic block copolymers leading to SB A materials ). Avoiding these conventional templates, Wei reported the preparation of mesoporous silica using glucose and Polarz succeeded in using cyclodextrins . 

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