Double-hydrophilic copolymers

Interpolyelectrolyte complexation between various charged (co)polymers or between charged double-hydrophilic copolymers and surfactants has been used as a tool to generate well-defined micellar structures, as will be discussed in more detail in Sect. 7.4. 

Similar IPEC-based aqueous micelles can be obtained from the mixing of a double-hydrophilic copolymer AB with a homopolymer C or a diblock copolymer AC or a diblock copolymer DC, provided that IPECs can form between the B and C blocks. This kind of electrostatic complex has also been referred to as block ionomer complexes, or BIC. 

Kataoka et al. [57, 58] investigated the formation of polyion complexes (PIC) from a pair of oppositely charged polypeptide block copolymers, namely of anionic poly(ethylene oxide)-( foc -poly(a, P-aspartate) and cationic polyethylene oxide)- foc -poly([2-aminoalkyl]-a,P-aspartamide) (see structure in Fig. 14a), in an aqueous milieu. Mixing of the double-hydrophilic copolymers at an equimolar... 

The synthesis of an ABA triblock double hydrophilic copolymer, where A= PEO and B= PSCl has been also reported via the utilization of chlorosulfonylisocyanate functionalization reaction on an anionically synthesized poly(ethylene oxide-b-isoprene-b-ethylene oxide) triblock precursor [11]. 

An important extension of anionic polymerization of acrylic monomers was the discovery of group-transfer polymerization (GTP), by Webster etal. [56], which allowed the synthesis of acrylic and methacrylic polymers in a Kving reaction at ambient temperature or above. A wide range of all-(meth) acrylic block copolymers as well hydrophilic-hydrophobic, as double-hydrophilic copolymers which are of special interest for micellization studies, could be prepared by Armes and co workers [57]. 

Typical examples of chemical modification leading to a wide range of hydrophobic-hydrophilic or double-hydrophilic copolymers is further the generation of PAA or PMAA blocks by selective hydrolysis of PtBA or PtBMA of block copolymers such as PS-b-PtBMA, PEO-b-PtBMA, etc. [75,76]. 

Further, the unique features of double-hydrophilic copolymers, cross-linked micelles, complex formation will be examined in the last part of this section. 

Typical examples of micelle formation in aqueous medium will be outlined in the following for these di- and triblock structures. Other examples of double-hydrophilic copolymers or with A-B-C structures, one of the blocks being PEO will be given in Sections 7.3.10 and 7.3.12. 

The self-association of double-hydrophilic copolymers of (meth)acrylic acid and PEO has recently been extended to PEO-b-P(EA-co-MMA) [220] and to triblock brush structures [221]. 

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