Hydrophilic/hydrophobic copolymers characterization

Ratner, B. D., Hoffman, A. S. Surface characterization of hydrophilic-hydrophobic copolymer model systems. I. A preliminary study, in Adhesion and Adsorption of Polymers, Part B (ed.) L. H. Lee, p. 691, New York, Plenum Press 1980... 

As described in Sec. 2, polymeric micelles that are formed through either hydrophilic-hydrophobic interaction of PEG-based block copolymers or electrostatic interaction of PE G-polycation block copolymers with negatively charged macromolecules have attracted considerable attention in the field of drug delivery and gene delivery systems, owing to their excellent biocompatibility, long blood circulation time, and nontoxicity. In this section, the preparation and the characterization of end-functionalized polymeric micelles... 

Mori, H., Hirao, A., Nakahama, S., Senshu, K. Synthesis and surface characterization of hydrophilic-hydrophobic block copolymers containing poly(2,3-dihydroxypropyl methacrylate). Macromolecules 27, 4093 100 (1994)... 

ATRP is probably the most utilized CRP technique for the synthesis of graft copolymers via the grafting through process. ATRP has been used by a number of groups to polymerize or copolymerize hydrophilic monomers or maaomonomers, including co-methacryloyloxy-PEO maaomonomers. Many efforts have been devoted over the years to design copolymers characterized by a hydrophobic backbone (PS, PMMA) and... 

Yu X, Roy A, Dunn S, Yang J, McGrath JE (2006) Synthesis and characterization of suUbnated-fluorinated, hydrophilic-hydrophobic multiblock copolymers for proton exchange membranes. Macromol Symp 245/246 439... 

Li Y, Roy A, Badami AS, Hill M, Yang J, Dunn S, McGrath JE (2007) Synthesis and characterization of partially fluorinated hydrophobic-hydrophilic multiblock copolymers containing sulfonate groups for proton exchange membrane. J Power Sources 172 30... 

In a very recent set of papers [48,54,59,60,131,132,324-328], the synthesis and characterization of metallosupramolecular amphiphilic block copolymers containing a hydrophilic PEO block linked to a hydrophobic PS or PEB block through a fozs-2,2/ 6/,2/terpyridine-ruthenium(II) complex have been described. These copolymers form the so-called metallosupramolecular micelles . 

The designed set of 2-oxazoline monomers that was used for the synthesis of the triblock copolymers (MeOx, EtOx, PheOx, and NonOx) yielded polymers of different polarity [91], P(MeOx) and P(EtOx) are hydrophilic, whereas P(PheOx) and P(NonOx) are hydrophobic. All possible combinations of these four different monomers would result in 64 different structures. However, all polymers that would have two times the same block after each other were excluded since they do represent diblock copolymers. Additionally, some structures, which have NonOx as the first block and EtOx or MeOx as the second block, were excluded due to extensive side reactions. Consequently, 30 different triblock copolymers were synthesized, and they are listed in Table 13 with their corresponding structural characterization. 

Recently, a new class of inhibitors (nonionic polymer surfactants) was identified as promising agents for drug formulations. These compounds are two- or three-block copolymers arranged in a linear ABA or AB structure. The A block is a hydrophilic polyethylene oxide) chain. The B block can be a hydrophobic lipid (in copolymers BRIJs, MYRJs, Tritons, Tweens, and Chremophor) or a poly(propylene oxide) chain (in copolymers Pluronics [BASF Corp., N.J., USA] and CRL-1606). Pluronic block copolymers with various numbers of hydrophilic EO (,n) and hydrophobic PO (in) units are characterized by distinct hydrophilic-lipophilic balance (HLB). Due to their amphiphilic character these copolymers display surfactant properties including ability to interact with hydrophobic surfaces and biological membranes. In aqueous solutions with concentrations above the CMC, these copolymers self-assemble into micelles. 

Synthesis and Characterization. The transition temperature (Tc) of NIPAAm copolymers can be modified by a hydrophilic or hydrophobic comonomer. This phenomenon has already been explained on the basis of inter-molecular and intramolecular hydrogen bond formation between the solvent (water) and polymer chains [6,7],... 

Figure 47.2. Pluronic block copolymers with various numbers of hydrophilic EO (n) and hydrophobic PO (m) units are characterized by distinct hydrophilic-lipophilic balance (HLB). Due to their amphiphilic character these copolymers display surfactant properties including ability to interact with hydrophobic surfaces and biological membranes. In aqueous solutions at concentrations above critical micelle concentration (CMC) these copolymers self-assemble into micelles.

Compared to low molecular weight amphiphiles, the size of polymeric amphi-philes allows for much more diverse arrangements of the hydrophilic and hydrophobic segments, as exemplified in Fig. 1. Accordingly, micellar polymers are characterized by versatile molecular architectures, giving rise to distinct subgroups. Diblock-copolymers with a clear separation of the hydrophilic... 

Another type of polypeptide-containing block copolymer, amphiliphilic rod-coil diblock copolymers such as poly (/V-triflu-oroacetyl-L-lysine)-/>-sarcosine) (Kt - Sa), were also synthesized and characterized by Gallot and coworkers [47]. The hydrophobic rod block poly(A-trifluoroacetyl-L-ly-sine) (Kt) was prepared by polymerization of Kt-NCA using A-hexylamine as the initiator. After fractionation using DMF (good solvent)/water (nonsolvent), the narrowly dispersed polymer (Kt) was then used as macroinitiator to initiate polymerization of the second monomer (Sa-NCA) to afford the hydrophilic block. Final elimination of Kt and Sa homopolymers were performed by precipitation with acetone and water respectively. The synthesis of Kt-Sa diblock copolymer is shown in Scheme 3. 

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