PEG block copolymer

Depending on the choice of transfer agent, mono- or di-cnd-functional polymers may be produced. Addition-fragmentation transfer agents such as functional allyl sulfides (Scheme 7.16), benzyl ethers and macromonomers have application in this context (Section 6.2.3).212 216 The synthesis of PEG-block copolymers by making use of PEO functional allyl peroxides (and other transfer agents has been described by Businelli et al. Boutevin et al. have described the telomerization of unsaturated alcohols with mercaptoethanol or dithiols to produce telechelic diols in high yield. 

Amino acid substitutions on the native y52 8sKIpeptide, coiled-coil domain of human fibrin were able to stabilize the coiled-coil formation. These substitutions were targeted to the positions that compose the interface between coiled-coil strands while the solvent-exposed residues were left unperturbed. This strategy aimed at reducing the likelihood of immunogenicity for future in vivo apphcafion of these materials. In contrast to PEG block copolymers with end blocks that are not used for directed assembly, PEG copolymers with coiled-coil protein motives aim to enhance intermolecular interactions and control over the assembly conditions [85, 173]. 

JH NMR data showed that the methyl peak of PPG is broadened in the presence of [S-CD, which suggests an interaction between [S-CD and the PPG s methyl group. We also remark that a PEG-PPG-PEG block copolymer com-plexed with [S-CD obeying the 2 1 stoichiometry. 

Lee ES, Shin HJ, Na K et al (2003) Poly(L-histidine)-PEG block copolymer micelles and pH-induced destabilization. J Control Release 90 363-374... 

Polyamide-polyether (PA-PEG) block copolymers have been studied using deuterated water (2H20) molecules as 2H NMR probes [85, 86, 87]. Well resolved doublets are observed on 2H20 on stretching the samples at room temperature. At a given elongation ratio X, the splitting depends on the water concentration c. The linewidth is that of a liquid and becomes comparable to that in bulk water for c=0.6. This confirms that water... 

Figure 15.16 2H NMR splittings in deuterated water molecules in a PA-PEG block-copolymer versus the stretching functions (a) or A, 2-A, 1 (b) (see Section 15.5.3.1), at various water concentrations c (the points at c = 0% are deduced from the measured splittings A(c) by extrapolation)...

Interestingly, when heated above the LCST, poly(NIPAAm)-PEG block copolymers spontaneously self-assemble into nanoparticles whose size is controlled by the rate of heating [132],... 

SANS in combination with contrast variation has been used to study the internal (core-shell) structure of nanoparticles prepared from amphiphilic PLA-poly(oxyethylene) glycol (PLA-PEG) block copolymer assemblies intended for use as nanoparticulate drug carriers. Three copolymers were synthesized with a constant PEG molecular weight of 5 kDa and a deuterated PLA chain of either 3, 15, or 45 kDa and nanoparticles... 

The PDEA-PEG block copolymer was synthesized by a typical atom-transfer radical polymerization (ATRP) using PEG as the macroinitiator (Scheme 10.4). This block copolymer formed micelles with diameters less than lOOnm, which is ideal for endocytosis. The dissolution of the micelles at low pH was monitored using A-phenyl-2-naphthylamine (PNA) as a florescent probe which has a low fluorescent activity in hydrophilic environments. The PDEA-PEG micelle was loaded with PNA. Its flnorescence was monitored as a fnnction of the solution pH. Eigure 10.18 suggests that the micelles dissolved at a pH about 6.0, which implies that the nanoparticles can... 

Peptide-poly(ethylene glycol) (PEG) block copolymers are ofparticiflar interest, both from a structural and a functional point of view. Poly(ethylene glycol) is also often referred to as poly(ethylene oxide) (PEG). Throughout this article, however, this polyether will be referred to as PEG. In contrast to the hybrid block copolymers discussed in the previous paragraphs, which were based on amorphous synthetic polymers, PEG is a semi-crystalline polymer. In addition to microphase separation and the tendency of the peptide blocks towards aggregation, crystallization of PEG introduces an additional factor that can influence the structure formation of these hybrid block copolymers, furthermore, PEG is an FDA approved biocompatible polymer, which makes peptide-PEG hybrid block copolymers potentially interesting materials for biomedical applications. 

Figure 3.46. DSC cooling and heating curves for the PEG-PI-PEG block copolymer, a pure PEG sample, and PI the homogeneous crystallization of the PEG segment at much higher degrees of undercooling does not really influence its melting behavior [RobitaUle and Prud homme, 1983],...

FUNCTIONALIZED POLYMERIC MICELLES BY A SELF-ASSEMBLING OF END-FUNCTIONALIZED PEG BLOCK COPOLYMERS... 

Aqueous solutions of high-PEG block copolymers possess a unique temperature-dependent reversible gel-sol transition. This allows hydrogels to be loaded with bioactive molecules, such as insulin, in an aqueous phase above the gel-sol transition temperature, usually around 45°C. As a sol, the insulin-loaded copolymer system is injectable. Upon exposme to the subcutaneous... 

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