Alternating copolymers poly

Alternating copolymer Poly(A-fllt-B) e.g., Poly(ethylene-a/t-tetrafluoroethylene)... 

T-Hg +-T interstrand cross-linking can occur in the alternating copolymer poly(dA-T) poly(dA-T), but not within or between homopolymeric strands in poly(dA) poly(T). The related complex [Hg(l-methyl-T)2] in which Hg + ion coordinates the deprotonated N-3 atoms of two pyrimidine residues, has been described as well. ... 

Alternating sulfobetaine copolymers were reported for 27 with SO2 [76], by analogy with the carbobetaine analogues described above. A very different approach was chosen for the alternating copolymer poly(ampholyte-electrolyte) 37, by condensing sodium 3-(pyrrol-l-yl) propanesuhbnate with squaric acid [77]. 

The high degree of specificity in the relationship between the conformations accessible to a particular DNA molecule and its nucleotide sequence is well illustrated by the occurrence of the D and S forms. The A, B and C forms have been observed with all naturally occurring DNAs which have been studied and also with both the alternating copolymers poly d(A-T).poly d(A-T) and poly d(G-C).poly d(G-C). However the D form but not the S form has so far only been observed with poly d(A-T).poly d(A-T) and conversely the S form but not the D form has been observed with poly d(G-C).poly d(G-C) but not with poly d(A-T).poly d(A-T). 

Direct copolymerization [1, 2], In this case, two types of monomers react, one of them having a functional or pendant functional group for instance, the copolymerization of maleic anhydride (MA) and styrene (St) generates the alternating copolymer poly (St-a/t-MA) [1]. Another example is the direct copolymerization of a-olefins (polypropylene, PP, and polyethylene. 

The importance of the conformational requirements outlined above can be illustrated by the stepwise degradation of the alternating copolymer poly r(F-U). When poly r(F-U) is exposed to RNase, it is first degraded to FpUp and then to 2, 3 -cyclic FMP and Up. In the two-stranded molecule formycin has the normal anti conformation. As such they are not acceptable substrates for RNase and the polymer is cleaved only at the uridine residues to yield FpUp. Once they are freed from the constraints imposed by the polymer structure, the formycin residues in these dinucleotides can assxime the syn conformation, whereupon they are attacked by the enzyme. 

The different copolymers with constitutional repeating units A and B are named according to the source-based nomenclature rules as follows unspecified type, poly(A-co-B) statistical copolymer, poly(A-stat-B) alternating copolymer, poly(A-a7f-B) graft copolymer, poly(A-gra/it-B). Note that the constitutional repeating unit of the backbone chain of the graft copolymer is specified first. 

Kirci B, Lutz J-P, Matyjaszewski K. Synthesis of weU-defined alternating copolymers poly(methyl methacrylate-alf-styrene) by RAFT polymerization in the presence of Lewis acid. Macromolecules. 2002 35 2448-2451. 

An alternating copolymer of a-methyl styrene and oxygen as an active polymer was recently reported [20]. When a-methyl styrene and AIBN are pressurized with O2, poly-a-methylstyreneperoxide is obtained. Polymerization kinetic studies have shown that the oligoperoxides mentioned above were as reactive as benzoyl peroxide, which is a commercial peroxidic initiator. Table 1 compares the overall rate constants of some oligoperoxides with that of benzoyl peroxide. 

Synthesis of strictly alternating copolymers can be achieved via various polymerisation techniques including poly-condensation or Ziegler-Natta polymerisations [123, 124]. 

Experimental studies of the adsorption of polyelectrolyte have been reported by several authors Pefferkom, Dejardin, and Varoqui (3) measured the hydrodynamic thickness of an alternating copolymer of maleic acid and ethyl vinyl ether adsorbed on the pore walls in cellulose ester filter as a function of the molecular weight and the concentration of NaCl. Robb et al. (4) studied the adsorption of carboxy methyl cellulose and poly (acrylic acid) onto surfaces of insoluble inorganic salts. However, their studies are limited to the measurements of adsorbance and the fraction of adsorbed segments. 

A similar technique was applied to the synthesis of AB and ABA block copolymers containing random and alternating copolymer sequences [178-180]. For example poly(St-ra dora-MMA)-hZock-poly(VAc), poly(VAc-hZock-poly(St-ran-dora-MMA)-hZock-poly(VAc), poly(St)-foZoc/c-poly(DiPF-aZMBVE), poly(IBVE-aZf-MAn)-hZock-poly(St)-hZock-poly(IBVE-aZf-MAn), poly(St)-hZock-poly(EA)-random-AA), and poly(St)-hZock-poly(EA-ra dora-AA-random-MMA) were synthesized [178]. 

Finally, these particles generated in ionic liquids are efficient nanocatalysts for the hydrogenation of arenes, although the best performances were not obtained in biphasic liquid-liquid conditions. The main importance of this system should be seen in terms of product separation and catalyst recycling. An interesting alternative is proposed by Kou and coworkers [107], who described the synthesis of a rhodium colloidal suspension in BMI BF4 in the presence of the ionic copolymer poly[(N-vinyl-2-pyrrolidone)-co-(l-vinyl-3-butylimidazolium chloride)] as protective agent. The authors reported nanoparticles with a mean diameter of ca. 2.9 nm and a TOF of 250 h-1 in the hydrogenation of benzene at 75 °C and under 40 bar H2. An impressive TTO of 20 000 is claimed after five total recycles. 

S.-H. Jin, M.-Y. Kim, D.-S. Koo, and Y.-I. Kim, Synthesis and properties of poly(fluorene-a/t-cyanophenylene vinylenej-based alternating copolymers for light-emitting diodes, Chem. Mater., 16 3299-3307, 2004. 

J.K. Herrema, P.F. van Hutten, R.E. Gill, J. Wildeman, R.H. Wieringa, and G. Hadziioannou, Tuning of the luminescence in multiblock alternating copolymers. 1. Synthesis and spectroscopy of poly[(silanylene)thiophene]s, Macromolecules, 28 8102-8116, 1995. 

Another class of "chain scission" positive resists is the poly(olefin sulfones). These polymers are alternating copolymers of an olefin and sulfur dioxide. The relatively weak C-S bond is readily cleaved upon irradiation and several sensitive resists have been developed based on this chemistry (49,50). One of these materials, poly(butene-l sulfone) (PBS) has been made commercially available for mask making. PBS exhibits an e-beam sensitivity of 1.6 pC cm-2 at 20 kV and 0.25 pm resolution. 

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