Oligomers and polymers

A mixture of the hydroxyborazine derivatives 1,3,5-(2-CH3C6H4)3-2-OH-4,6- (CH3)2-B3N3 and 1,3,5-(2-CH3C6H4)3-2,4-(0H)2-6-CH3-B3N3 is obtained by careful partial hydrolysis of [-B(Cl)-N(C6H4CH3-2)-]3 [54]. 

5-(CH3)3-2-X-B3N3H2 with X = N(C4H9-f)-BH-NC9Hi8 is formed in the reaction of 2,2,6,6-tetramethylpiperidin-1-ylamino-f-butyliminoborane with 1,3,5-trimethylborazine (C9HiqN = 2,2,6,6-tetramethylpiperidin-1-yl) [58]. 

B5N5H8 and BeNgHio. the BN analogues of naphthalene and biphenyl, have been observed in the mass spectrum of thermal decomposition products of poly(aminoborane), (-BH2-NH2-)x, under Cl conditions [59]. The structure of various formulations of polycondensates obtained from trimethylsilanyl-substituted 2,4,6-triaminoborazine derivatives (see Section 4.2.3.3, p. 186) are primarily based on thermogravimetry and IR spectroscopy [32, 34]. 

The dimers of type 47 and the B-N-bonded polymers 46 and 48 have been prepared from the corresponding B-chloroborazines and HN[Si(CH3)3]2 or H3CN[Si(CH3)3]2. They are useful as poly(borazinylamine) precursors for boron nitride ceramics [60, 61]. 

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Pure D-fmctose is a white, hygroscopic, crystalline substance and should not be confused with the high fmctose com symps (HFCS) which may contain 42—90 wt % fmctose and 23—29% water (8,9). The nonfmctose part of these symps is glucose (dextrose) plus small amounts of glucose oligomers and polymers. Fmctose is highly soluble ia water at 20°C it is 79% soluble, compared with only 47% for glucose and 67% for sucrose. 

The UF-resin itself is formed in the acid condensation step, where the same high molar ratio as in the alkaline methylolation step is used (F/U = 1.8 to 2.5) the methylolureas, urea and the residual free formaldehyde react to form linear and partly branched molecules with medium and even higher molar masses, forming polydispersed UF-resins composed of oligomers and polymers of different molar m.asses. Molar ratios lower than approx. 1.7-1.8 during this acid condensation step might cause resin precipitation. 

In these reactions the system is tuned, for example by adjustment of the reaction temperature and time and modification of the catalyst structure to maximize the quantity of the desired dimers produced, and to minimize the production of higher molecular weight oligomers and polymers. In other reactions it is the opposite... 

Acyclic diene molecules are capable of undergoing intramolecular and intermolec-ular reactions in the presence of certain transition metal catalysts molybdenum alkylidene and ruthenium carbene complexes, for example [50, 51]. The intramolecular reaction, called ring-closing olefin metathesis (RCM), affords cyclic compounds, while the intermolecular reaction, called acyclic diene metathesis (ADMET) polymerization, provides oligomers and polymers. Alteration of the dilution of the reaction mixture can to some extent control the intrinsic competition between RCM and ADMET. 

The synthesis-driven approach towards material science can be applied to create oligomers and polymers with optimized properties, e.g. maximized carrier mobilities and electrical conductivities or high photo- and electroluminescence quantum yields. It becomes obvious, however, that the ability to synthesize structurally defined -architectures is the key to these high performance materials. 

This article, while not being intended to provide a full account of poly(arylene)s, emphasises the synthetic aspects. The synthesis of conjugated oligomers and polymers is, however, always part of an interdisciplinaiy approach with their active physical function being a key concern. In that sense the research being reviewed above concentrates on physical properties rather than playing with exotic chemical structures. 

Finally, we would like to point that one of the easiest ways to influence the electronic properties of conjugated oligomers and polymers is to vary the chain... 

The polaron is characterized by the reversal of bond alternation, which, in the case of polythiophene, extends over five monomer units [30-32], and the appearance of two localized stales in the band gap ). These states have been indeed observed by UV-V1S absorption of both oligomers and polymers, in solution [33— 40] and in the solid state [41-45]. 

The results presented up to here concern only one-dimensional oligomers and polymers of the PPP-lype. This section is mainly focussed on the electronic properties of extended re-chains and on the morphology of solid PPPs using chain-stiffness as a structure-forming principle for supramolecular architectures. 

Pospisil, J. Functionalized Oligomers and Polymers as Stabilizers for Conventional Polymers. Vol. 101, pp. 65-168. 

Thio- and seleno-compounds of the main group elements — novel inorganic oligomers and polymers. B. Krebs, Angew. Chem., Int. Ed. Engl., 1983, 22,113-134 (252),... 

The study of plutonium hydrolysis is complicated by the formation of oligomers and polymers once the simple mononuclear hydrolysis species start forming. The relative mono-oligomer concentrations are dependent on the plutonium concentration - e.g. the ratio of Pu present as (Pu02)2(0H)22 to that as PuO2(0H)+ is 200 for [Pulx = 0.1 M, 5.6 for 10-1 M and 0.05 for 10 8 M. 

The monocyclic 1,4-diazepine, l,4-diaza-S,7-cycloheptanedione, has in the past been reported to have been formed by the reaction of 1,2-diaminoethane with various malonic acid derivatives. It is now claimed that this derivative has never been formed, and may never be formed <96JPR121>. Oligomers and polymers are the sole products. However, reaction of... 

From a practical stand point almost any of the lower-molecular weight vinyl monomers, cross-linking oligomers, and polymers can be blended with a high-molecular weight thermoplastic polymer to enhance cross-link density at lower dose rates [39]. The influence of various other additives on the efficiency of cross-linking of polymers will be highlighted in the subsequent sections. 

Chapter 5, written by M. Hissler, P. W. Dyer, and R. Reau, concerns an area of important expansion, i.e., the synthesis and properties of rr-conjugated oligomers and polymers containing phosphorus moieties. The possibility of using... 

The anionic method of polymerization is most useful for the synthesis of low molecular weight hydroxy-terminated oligomers and polymers that are to be further processed. For example, the treatment of hydroxy-terminated oligomers with isocyanates has been used to obtain polyester-urethanes (9,20), while triblock copolymers (PCL-PEG-PCL) are prepared by initiating the polymerization of e-caprolactone with the disodium alcoholate from polyethylene glycol (26). 

D. J., Organosilylphosphazene oligomers and polymers Synthesis via lithioaryloxyphosphazenes, Macromolecules. 22. 3571, 1989. 

This article summarizes efforts undertaken towards the synthesis of the cyclo[ ]carbons, the first molecular carbon allotropes for which a rational preparative access has been worked out. Subsequently, a diversity of perethynylated molecules will be reviewed together, they compose a large molecular construction kit for acetylenic molecular scaffolding in one, two and three dimensions. Finally, progress in the construction and properties of oligomers and polymers with a poly(triacetylene) backbone, the third linearly conjugated, non-aromatic all-carbon backbone, will be reviewed. 

Molecular Wires Oligomers and Polymers with the Poly(triacetylene) (PTA) Backbone... 

Scheme 8. Oligomers and polymers with a poly(triacetylene) (PTA) backbone that are derived from tetraethynylethenes (TEEs)...

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