Homopolymer complexes

Among the two ionic polymerization techniques mentioned above, a living anionic polymerization should show the best possible control of polymer architecture and composition. Mono dispersed homopolymers, complex-block, graft, star, and miktoarm architectures have been accessible primarily by anionic polymerization methods [22]. They have been used to grow polymer brushes from various small particles such as silica gels graphite,carbon black, and flat surfaces [23-26]. Recent results have been reported on living anionic polymerizations on clay [27] and silica nanoparticles [28,29]. 

Helices formed by homopolymer complexes can be parallel or antiparallel,... 

Properties of Solutions of Homopolymer Complexes Stabilized by Hydrogen Bonds... 

The following features of homopolymer complexes stabilized by the system of hydrogen bonds have been observed5,27>33-36-39-42-54) (Table 2) ... 

The poly(methacrylic acid)-polyvinylpyrrolidone system have been studied in detail in the series of the homopolymer complexes investigated by the authors (Table 2). The possibility of complex formation in this system has been shown by potentiometry, conductometry and viscometry and also by IR spectroscopic and thermogravimetric investigations of PMAA-PVP complexes in the solid state27,57). 

The stability of the complexes to temperature, ionization and solvent nature has been investigated. The copolymer complexes turned out to be much less stable than the homopolymer complexes. In general, the compact structure of these complexes is as a rule destroyed at a lower content of organic solvent in the mixture. 

Thus, the experimental results show that the macromolecules with disturbed complementarity retain the ability for complex formation. The formed complexes display all properties which are characteristic of homopolymer complexes in solution. 

Homopolymer, complex with 5 -cytidylic acid polymer with 5 -uridylic acid (1 1) AmpUgen. Oragen. Poly (I) Poly (CuV)... 

In each section double stranded complexes are shown first, followed by triple stranded complexes. Strands 1 and 2 are considered to be Watson-Crick hydrogenbonded and thus anti-parallel, except otherwise indicated. In the triple-strand case the Hoogsteen bound strand is strand 3 and thus parallel to strand 1. In the homopolymer complexes the strands are generally parallel. 

Note that the hybrid homopolymer complex always melts at a lower temperature than either the all-ribo or the all-deoxyribo complex also, the all-ribo complex is thermally the most stable. It should be noted that DNA-RNA hybrid structures melt at a temperature about 4 lower than that for DNA itself, which, in turn, has a considerably lower Tm than a double-stranded RNA with the same base composition. Similar observations are made for the G-C and l-C series (see below). 

The alternating deoxypolymers poly(dl-dC) and poly(dG-dC) are thermally more stable than the homopolymer complexes, an apparently general finding. 

In block copolymer or block copolymer/homopolymer complex systems, core/shell micelles with unicompartmental corona have been observed so far. Systems involving complexes of two block copolymers have an opportunity to form compartmentalized corona due to difference in hydrogen-bonding strength between two coronal blocks. 

Hameed N, Salim NV, Guo Q. Microphase separation through competitive hydrogen bonding in self-assembled A-b-B/C diblock copolymer/homopolymer complexes. J Chem Phys 2009 131(21) 214905-214905. 

Salim NV, et al. Microphase separation induced by competitive hydrogen bonding interactions in semicrystalline triblock copolymer/homopolymer complexes. Soft Matter 2013 9(26) 6176-84. 

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