Amphiphilic triblock polymers

Zhao et al. (1998a, b) reported the use of amphiphilic triblock polymers such as polyethylene oxide-polypropylene oxide-polyethylene oxide in combination with tetraethoxysilane as the silica source. The OMS stmcture obtained by this method is known as SBA-15 with a pore size of around 30 nm and a wall thickness similar to MCM-41. SBA-15 is proven to be comparatively better for tablet dosage forms because it is better at withstanding compression forces encountered in tableting (Qian and Bogner2012). 

More precisely defined self-assembly systems than those described in the previous section can be prepared from block copolymers. For example, an amphiphilic polyphosphazene diblock based on roughly equal proportions of [N=P(0CH2CH20CH2CH20CH3)2] , as a hydrophilic block, and [N=PPh(0CH2CH20CH2CH20CH3)] , showed a critical micelle concentration (CMC) of 80 mg/L in an aqueous solution [60], whilst the lower CMC values of 12.4 and 5.2 mg/L are reported for polyethylene oxide-block-poly[bis(trifluoroethoxy)phosphazene]s depending on the block length. Amphiphilic triblock polymers with PPG of the same polyphosphazene showed similar self-assembly behaviour with CMC values in a comparable range [56]. 

Even, M., Haddleton, D.M., Kukulj, D. Synthesis and characterization of amphiphilic triblock polymers by copper mediated hving radical polymerization. Eur. Polym. J. 39(4), 633-639 (2003)... 

Uchegbu and coworkers have studied the complexation and delivery of DNA using a unique poly(amino acid)-based polymer vesicle. A polymer of either poly (L-lysine) or poly(L-omithine) was functionalized with methoxy-poly(ethylene glycol) (mPEG) and hydrophobic palmitic acid chains to synthesize an amphiphilic triblock of either mPEG-6-poly(L-lysine)-6-palmitoyl or mPEG-Z>-poly(L-omithine)-6-palmitoyl. Vesicles formed from these polymers were complexed with DNA and showed improved transfection in vitro over poly(amino acid) complexed with DNA or DNA alone [82]. 

Encapsulation and delivery of DNA has also been investigated with poly(amino acid) (poly(AA)) based polymer vesicles. Brown and coworkers synthesized an amphiphilic triblock copolymer from methoxy-poly(ethylene glycol) (mPEG), hydrophobic palmitic acid chains in block segments along a poly-L-lysine (PLL) or... 

Planar polymer films (either free-standing or at interfaces) are of particular interest, not only because they are preferred in many applications, but also because they allow for surface studies which could not be performed on vesicles. Langmuir monolayers from a vesicle-forming amphiphilic triblock copolymer were studied towards understanding the polymer interactions with a cation transporting peptide, alamethicin [275]. Planar solid supported block copolymer membranes are... 

Poly( ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) is another kind of thermosensitive polymer, known as poloxamer (25,26). Poloxamers are a series of surfactant polymers that are commercially available. Among these, poloxamer 407 (Pluronic F127) has been of particular interest, since this amphiphilic triblock copolymer can form micelles at low concentration in water and, with increasing concentration, can form a hydrogel at body temperature via... 

Wittemann A, Azzam T, Eisenberg A (2007) Biocompatible polymer vesicles from bi-amphiphilic triblock copolymers and their interaction with bovine serum albumin. Langmuir 23 2224-2230... 

Marimuthu, M., Kim, S.J., 2010. Spontaneous extmsion of porous amphiphilic triblock copolymeric microfibers under microfluidic conditions. Polym J 42, 100—102. 

Tang X, Gao L, Fan X, Zhou QF. 2007. ABA type amphiphilic triblock copolymers containing p ethoxy azobenzene via atom transfer radical polymerization synthesis, characterization, and properties. J Polym Sci Part A Polym Chem 45 2225 2234. 

Tan J, Brash JL. Nonfouling biomaterials based on polyethylene oxide-containing amphiphilic triblock copolymers as surface modifying additives synthesis and characterization of copolymers and surface properties of copolymer-polyurethane blends. J Appl Polym Sci 2008 108 1617-28. 

Yang, Z., Yuan, J., and Cheng, S. (2005) Self-assembling of biocompatible BAB amphiphilic triblock copolymers PLL(Z)-PEG-PLL(Z) in aqueous medium. European Polymer Journal, 41,261-21 A. 

Narumi A, Matsuda T, Kaga H, Satoh T, Kakuchi T (2002) Synthesis of amphiphilic triblock copolymer of polystyrene and poly(4-vinylbenzyl glucoside) via TEMPO-mediated living radical polymerization. Polymer 43(17) 4835 840... 

Yuan L, Chen W, Li J, Hu J, Yan J, Yang D. PEG-i>-PtBA-f>-PHEMA weU-defined amphiphilic triblock copolymer synthesis, self-assembly, and apphcation in drug dehvery. J Polym Sci, Part A Polym Chem 2012 50 4579-88. 

Figure 7.9 An amphiphilic ABA triblock polymer capped with Qo at both ends.

This polypeptide is structurally identical to ABA-type triblock copolymer with a central hydrophdic elastomeric end-block capped with two hydrophobic plastic end-blocks and exhibits amphiphilic characteristics. The end-blocks of the polymer were chosen in such a way that their LCST would reside at or near room temperature. Thus the polymer exhibits phase separation, which is analogue to conventional TPEs, and offers TPE gels under physiological relevant conditions [104]. Glutamic acid residue is placed periodically in the elastomeric mid-block to increase its affinity towards the aqueous... 

Some other degradable (i.e., nonvinyl-type) polymers have been reported as components for amphiphilic block copolymers. For example, Hsiue reported the synthesis of a block copolymer of poly(2-ethyl oxazoline) and PLA by ROP. They reported the use of ABA-type triblock copolymers as pH-responsive polymer... 

---