Cationic amphiphilic copolymers

Dautzenberg et al. reported on an alternative method to produce cationic amphiphilic block copolymers starting from a poly(vinylbenzyl) precursor block, which was then converted into a cationic polyelectrolyte by reaction with tertiary amines [162],... 

To synthesize water-soluble or swellable copolymers, inverse heterophase polymerization processes are of special interest. The inverse macroemulsion polymerization is only reported for the copolymerization of two hydrophilic monomers. Hernandez-Barajas and Hunkeler [62] investigated the copolymerization of AAm with quaternary ammonium cationic monomers in the presence of block copoly-meric surfactants by batch and semi-batch inverse emulsion copolymerization. Glukhikh et al. [63] reported the copolymerization of AAm and methacrylic acid using an inverse emulsion system. Amphiphilic copolymers from inverse systems are also successfully obtained in microemulsion polymerization. For example, Vaskova et al. [64-66] copolymerized the hydrophilic AAm with more hydrophobic methyl methacrylate (MMA) or styrene in a water-in-oil microemulsion initiated by radical initiators with different solubilities in water. However, not only copolymer, but also homopolymer was formed. The total conversion of MMA was rather limited (<10%) and the composition of the copolymer was almost independent of the comonomer ratio. This was probably due to a constant molar ratio of the monomers in the water phase or at the interface as the possible locus of polymerization. Also, in the case of styrene copolymerizing with AAm, the molar fraction of AAm in homopolymer compared to copolymer is about 45-55 wt% [67], which is still too high for a meaningful technical application. 

Figure 3.3 Synthesis of methacrylate random copolymers with cationic amphiphilic structures containing R hydrophobic groups (methyl, ethyl, butyl, hexyl and benzyl groups). AIBN azobisisobutylonitrile, RT room temperature and TFA trifluoroacetic acid. Reprodnced with permission from H. Takahashi,...

In this study, the authors investigate the living cationic polymerization of polar monomers in the presence of added bases to prepare living polymers of various properties and shapes. Based on the results, various types of amphiphilic copolymers are designed, and the stimuli-induced self-association of the products, such as thermosensitive physical gelation, is characterized. 

The hydrophilic, hydrophobic, and ionic nature of PVP can be modified by copolymerization to enhance the properties of PVP for certain applications. Nonionic, anionic, and cationic VP copolymers have all been commercialized. A wide range of vinyl pyrrolidone and vinyl acetate copolymers, which are non-ionic, have been made with optimized amphiphilicity and solubility in water or alcohol for the cosmetic and pharmaceutical industries. The surface activity of PVP can be further enhanced by copolymerization with acrylic acid. Vinyl pyrrolidone and acrylic acid copolymers, which are anionic in their major applications, with different molar rations have been developed with well-balanced surface, associative, and film-forming properties for industrial applications. 

Well-Defined Amphiphilic Copolymers. Well-defined, controlled structure amphiphilic copol5miers may be prepared using a range of polymerization techniques that includes anionic, cationic, and controlled free radical approaches. The materials may be simple AB diblock copolymers or more structin-ally complex species such as ABA or ABC triblock copol5uners for example. 

Palermo E, Lee D, Ramamoorthy A, et al. The role of cationic group structure in membrane binding and disruption by amphiphilic copolymers. J Phys Chem B 2011 115(2) 366-75. 

Self-assembled ROMP copolymers were also considered for nonviral transfection of DNA. Emrick and Breitenkamp [71] reported the preparation of cationic amphiphilic graft copolymers by ROMP of COE macromonomers 22 (Scheme 2.11). The structure ofthe resulting product consisted of a hydrophobic PCOE backbone with pendant oligolysine grafts 23 (Scheme 2.11). 

Fischer, A., Brembilla, A., and Lochon, P. (2000). Synthesis of new amphiphilic cationic block copolymers and study of their behavior in aqueous medium as regards hydrophobic microdomain formation. Polymer, 42(A) 1441 1448. 

Amphiphilic and cationic triblock copolymers consisting of MPEG, PCL, and poly-12 (R=CH2CH2NH2) were also obtained. Cyclic phosphates (12) (R=Me, Et, Pd) were used to adjust the hydrophobic-hydrophilic balance of the copolymers and influence their thermosensitivity in a wide range. 

To make amino-group functionalized PPEs, which will be positively charged and therefore have potential for nucleic add delivery, the functional phosphoester monomer 2-(N-tert-butoxycarbonyla-mino)ethoxy-2-oxo-l,3,2-dioxaphospholane (PEEABoc) (17) has been synthesized. Based on the ROP of PEEABoc using hydroxyl-terminated MPEG-b-PGL as the macroinitiator, an amphiphilic and cationic triblock copolymer consisting of MPEG, PCL, and poly(2-aminoethyl ethylene phosphate) has been developed, which is denoted mPEG-b-PCL-f -PPE-EA (eqn [10]). This amphiphilic polymer can self-assemble into nanopartides in aqueous solution and absorb siRNA for RNAi-based therapy. 

Figure 11 shows Stern-Volmer plots for fluorescence quenching of the amphiphilic cationic copolymer QPh-x [74]. The quenching of QPh-x with MV2+ is expected to be much less effective than that of APh-x. The quenching data for the QPh-x system are presented in Table 3. For comparison, the data for a related... 

For some applications, it is desirable to lock the micellar structure by cross-Hnking one of the micellar compartments, as discussed previously in Sect. 2.6. Cross-Hnked core-shell-corona micelles have been prepared and investigated by several groups as illustrated by the work of Wooley and Ma [278], who reported the cross-linking of PS-PMA-PAA micelles in aqueous solution by amidation of the PAA shell. Very recently, Wooley et al. prepared toroidal block copolymer micelles from similar PS-PMA-PAA copolymers dissolved in a mixture of water, THF, and 2,2-(ethylenedioxy)diethylamine [279]. Under optimized conditions, the toroidal phase was the predominant structure of the amphiphilic triblock copolymer (Fig. 19). The collapse of the negatively charged cylindrical micelles into toroids was found to be driven by the divalent 2,2-(ethylenedioxy)diethylamine cation. 

Much research has already been devoted in the past couple of years to (i) the immobilization of ATRP active metal catalysts on various supports to allow for catalyst separation and reycycling and (ii) ATRP experiments in pure water as the solvent of choice [62]. A strategy to combine these two demands with an amphiphilic block polymer has recently been presented. Two types of polymeric macroligands where the ligand was covalently linked to the amphiphilic poly(2-oxazo-line)s were prepared. In the case of ruthenium, the triphenylphosphine-functiona-lized poly(2-oxazoline)s described in section 6.2.3.2 were used, whereas in the case of copper as metal, 2,2 -bipyridine functionalized block copolymers were prepared via living cationic polymerization [63] of 2-methyl-2-oxazoline and a bipyridine-functionalized monomer as shown in Scheme 6.8. 

Hoogenboom R, Wiesbrock F, Huang H et al. (2006) Microwave-assisted cationic ringopening polymerization of 2-oxazolines a powerful method for the synthesis of amphiphilic triblock copolymers. Macromolecules 39 4719-4725... 

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