Architecture, comb-like copolymers

A recent trend is to design polymers with multiple functions including cationic units to bind nucleic acids as well as pH-sensitive carboxylic acids for endosomal dismption. Using a block copolymer architecture, comb-like polymers with cationic grafts were extended from aspartic acid units via a hydrazone linkers.The second block was composed of... 

Reversible deactivated radical polymerization processes, which have been referred to as living/controlled radical polymerizations, allow for producing polymeric materials with controlled molecular masses, low dispersities, and complex maaomolecular architectures, such as block and comb-like copolymers as well as star-shaped (co)polymers. In addition to nitroxide-mediated polymerization (NMP) ° and atom-transfer radical polymerization (ATRP), ° reversible addition fragmentation chain-transfer (RAFT) polymerization is an attractive new method. " ... 

A similar evaluation was made for the other series of CA-g-PHAs to establish a general relationship between their molecular architecture and thermal transition behavior [24]. Of particular interest is the finding that the composition dependence of the Tg of the cellulosic graft copolymers was represented well in terms of a formulation based on a comb-like polymer model [29], when CAs of acetyl DS 2 were employed as a trunk polymer. 

Fig. 1 a—f. Various branched architectures obtained by the macromonomer technique a,b comb-like c,d star-like e brush f flower-like, a c, and e are poly(macromonomers) obtained by homopolymerization, while b, d, and f are graft copolymers obtained by copolymerization... 

WUG Wu, G., Chen, S.-C., Zhan, Q., and Wang, Y.-Z., Well-defined amphiphilic biodegradable comb-like graft copolymers Their rmique architecture-determined LCST and UCST thermoresponsivity. Macromolecules, 44, 999, 2011. 

In this work, poly(ethylene glycol) was grafted onto a cationic poly-L-lysine backbone, forming the comb-like polymer, poly(L-lysine)-graft-poly(ethylMie glycol) (PLL-g-PEG). The PLL backbone acts as an anchor onto anionic surfaces such as mica (Fig. 1 a). This type of copolymer exhibits an extraordinarily strong adsorption onto many different surfaces. Different PLL-g-PEG architectures are known to exhibit different degrees of protein resistance (Kenausis et al., 2000 Pasche et al., 2003). In this article, we have focused on the most efficient architecture for protein resistance. 

Gitsov, I. (2000) Hybrid dendritic capsules properties and binding capabilities of amphiphilic copolymers with dendritic architecture. In J.E. Glass (ed.), Associative Polymers in Aqueous Media, ACS Symposium Series 765. American Chemical Society, Washington, DC, pp. 72-92. Kurjata, J., Chojnowski, J., Yeoh, C.T., Rossi, N.A.A. and Holder, S.J. (2004) Synthesis of poly[dimethylsiloxane-block-oligo(ethylene glycol) methyl ether methacrylate] an amphiphilic copolymer with comb-like block. Polymer, 45,6111-6121. 

Fig. 2. Selected architectures of block copolymers (a) diblock (b) triblock (c) comb copolymer consisting of flexible chains (d) rod-coil diblock copolymer consisting of a rodlike block and a coil-like block (e) hairyrods, i.e., comb-block copolymers consisting of rodlike backbone and coil-like side chains and (f) LC coil with a side-chain liquid crystalline (LC) block and a flexible block. Many other variations have been introduced, such as multiblock copolymers, block copolymers consisting of several rodlike blocks, or star-shaped block copolymers. Comb-coil block copolymers with dense packing of side chains are also denoted as molecular bottle brushes, as is illustrated in (g) by a simulated structure of an isolated molecule dissolved in a solvent. (Courtesy of Mika Saariaho.)...

Cycloolefin macromonomers have been recently used in ring-opening metathesis polymerization reactions to manufacture block and graft copolymers of novel macromolecular architectures [84]. For this purpose, a- and co-norbornenyl-polybutadiene macromonomers, a-NBPB (R = CH2) and co-NBPB (R = COO), were reacted in the presence of molybdenum alkylidene complex, Mo(NAr)(CHtBu)(OtBu)2, to form polynor-bornene-polybutadiene diblock copolymers (117), with comb-like structure [85] [Eq. (49)]. 

Figure 19.23 Schematic diagrams of linear, Y-shaped, and comb-like rod-coil block copolymer brushes. (Reproduced with permission from C.-S. Li, W.-C. Wu, Y.-J. Sheng and W.-C. Chen Effects of chain architectures on the surface structures of conjugated rod-coil block copolymer, Journal of Chemical Physics, 128, 154908, 2008. 2008 American Institute of Physics.)...

In the following sections, we will review the various different ways in which comb copolymer-like architectures (supramolecular comb copolymers) mi t be obtained using noncovalent physical interactions, e.g., ionic, coordination complexation, or hydrogen bonding see Figure 8. 

Finally, in limited occasions, self-assembled aggregates with a bicontmuous structure have been reported. For example, in the case of a PS-PAA diblock copolymer in a water/DMF mixture [64], of PEO-PPO-PEO triblock copolymers in water or water/oil mixtures [65-67] and PAA-PMA-PS in water/THE mixture [68], or more complex chain architectures, like a Unear-comb [69] and a comb-comb [70] diblock copolymer, are considered. 

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