Poly , atactic synthesis

Abe H, Doi Y, Kumagai Y (1994a) Synthesis and characterization of poly[(R,S)-3-hydroxybu-tyrate-b-6-hydroxyhexanoate] as a compatibilizer for a biodegradable blend of poly[(R)-3-hydroxybutyrate] and poly(6-hydroxyhexanoate). Macromolecules 27 6012-6017 Abe H, Dd Y, Satkowski MM, Noda I (1994b) Miscibility and morphology of blends of isotactic and atactic poly(3-hydroxybutyrate). Macromolecules 27 50-54 Abe H, Matsubara I, Doi Y (1995) Physical properties and enzymic degradability of polymer blends of bacterial poly[(R)-3-hydroxybutyrate] and poly [(R,S)-3-hydroxybuty rate] stereoisomers. Macromolecules 28 844-853... 

Coates, G.W., Cheng, M., and Chamberlain, B.M. (2000) inventors (Cornell Research Foundation, Inc., USA), assignee. Synthesis of stereospecific and atactic poly(lactic acid)s using single-site catalysts. WO Patent US28886 2001034555, 2001 20001108. 

The random copolymerization (TrMA/DMA = 1/1) provides a valuable approach for the synthesis of atactic poly(methyl methacrylate) (At-PMMA). 

Figure 7. Neutron difference synthesis o/ atactic poly(vinyl alcohol). Broken and solid contour lines denote the heights with 0.0 and -1.0, respectively. (Reproduced with permission fi om reference 7. Copyright 1997, Wiley-InterScience)...

Neutron structure analyses were successfully carried out on two crystalline polymers, atactic poly(vinyl alcohol) and polyethylene-d4. Neutron structure analysis supports Bunn s model for atactic poly(vinyl alcohol). Three peaks found on the difference synthesis were assigned to the hydrogen atoms to be associated with the intra molecular hydrogen bond in an isotactic sequence of atactic polymer and the intermolecular hydrogen bonds. Neutron diffraction study clarified the detailed crystal structure of polyethylene, in which the azimuthal angle

molecular plane with respect to the b-axis is 45° within the accuracy of the standard deviation 1°. Furthermore, translational and librational motions of the molecule were estimated. The nature of the static disorder in polyethylene was also clarified. 

Simpler initiating systems based on the association of conventional anionic initiators, typically sodium or potassium alkoxides (ROMt), with trialkylaluminum (R3AI) behave very similarly to porphyrin salts associated to bulky Lewis acid systems. For instance, sodium isopropoxide in combination with triisobutylaluminum in hydrocarbon solvents yields rapid POx polymerization at room temperature or below." The chain transfer reactions are also strongly reduced in these conditions, thus allowing the synthesis of regioregular atactic poly(POx), with relatively high molar masses (up to SOOOOgmol" ). 

The poly(vinyl alcohol) made for commercial acetalization processes is atactic and a mixture of cis- and /n j -l,3-dioxane stereoisomers is formed during acetalization. The precise cis/trans ratio depends strongly on process kinetics (16,17) and small quantities of other system components (23). During formylation of poly(vinyl alcohol), for example, i j -acetalization is more rapid than /ra/ j -acetalization (24). In addition, the rate of hydrolysis of the trans-2iQ. -A is faster than for the <7 -acetal (25). Because hydrolysis competes with acetalization during acetal synthesis, a high cis/trans ratio is favored. The stereochemistry of PVF and PVB resins has been studied by proton and carbon nmr spectroscopy (26—29). 

Monomers Figure3.8 shows a small selection of cyclic monomers suitable for ROP [43]. Additionally, three different stereoisomers of lactide exist as a consequence of the presence of two stereocenters per monomer unit, namely meso-, L- and d-lactide, see Fig. 3.9. Further, racemic mixture of L- and D-lactide are commercially available. While ROP of either pure l- and D-lactide enables synthesis of highly crystalline poly(L-lactic acid) or poly(D-lactic acid), ROP of rac- or wcj< -lactide with adequate catalysts allows the synthesis of stereoblock copolymers, heterotactic and syndiotactic poly(lactic acid). Notably, stereoregular PLAs display much lower rates of degradation than the amorphous atactic polymer. 

Figure 16.15 TEM images for bulk state morphologies of PS- -PFS (a-c), PFS- -PMMA (d) and PMMA- -PFS-Z -PS-Z -PFS- -PMMA (e-f) (PFS = poly(ferrocenylethylmethylsilane) in (a)-(c) and the dimethyl analog in (d)-(f). ((a)-(c) Reprinted with permission from D.A Rider, K.A. Cavicchi, K.N. Power-Billard et al, Diblock copolymers with amorphous atactic polyferrocenylsilane blocks Synthesis, characterization, and self-assembly of polystyrene-block-poly(ferrocenylethylmethylsilane) in the bulk state, Macromolecules, 38, 6931, 2005. 2005 American Chemical Society, (d) Reprinted with permission from C. Kloninger and M. Rehahn, Bicontinuous gyroidic morphologies in ferrocenyldi-methylsilane-b-methyl methacrylate diblock copolymer blends, Macromolecules, 37, 8319, 2004. 2004 American Chemical Society, (e)-(f) Reproduced with permission from U. Datta and M. Rehahn, Synthesis and self-assembly of styrene-[l]dimethylsilaferrocenophane-methyl methacrylate penta-block copolymers, Molecular Rapid Communications, 2004,25,1615. Wiley-VCH Verlag GmbH Co. KGaA.)...

Rider, D.A., Cavicchi, K.A., Power-BiUard, K.N. et al. (2005) Diblock copolymers with ammphous atactic polyferrocenylsilane blocks synthesis, characterization, and self-assembly of polystyrene-block-poly(ferrocenylethyl-methylsilane) in the bulk state. Macromolecules, 38,6931. 

Poly(N,N-dimethylacrylamide) with controlled MW, low values for M /Mn, and a high proportion of meso dyads (approx. 85%) was prepared using ATRP (methyl 2-chloropro-pionate/CuCl/MeeTREN) and RAFT (with cumyl dithiobenzoate transfer agent) in the presence of Y(OTf)3. These systems were used for the first one-pot synthesis of stereoblock copolymers by RP. Well-defined stereoblock copolymers, atactic-l -isotactic poly(N,N-dimethylacrylamides), were obtained by adding Y(OTf)3 to either an ongoing RAFT or ATRP polymerization, started in the absence of the Lewis acid. "... 

Sakurai K., MacKnight W. J., Lohse D. J., Schulz D. N., and Sissano J. A. (1994) Blends of amorphous-crystalline block copolymers with amorphous homopolymers. 2. Synthesis and characterization of poly(ethylene-propylene) diblock copolymer and crystallization kinetics for the blend with atactic polypropylene. Macromolecules 27 4941-4951. 

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