Poly reaction pathway

TiCU readily functionalizes hydrophilic polymers such as poly(vinyl alcohol), m-ciesol novolac and methacrylic acid copolymers as well as moderately hydrophobic polymers such as poly(methyl methacrylate), poly(vinyl acetate), poly(benzyl methacrylate) and fully acetylated m-cresol novolac. HCI4 did not react with poly(styrene) to form etch resistant films indicating that very hydrophobic films follow a different reaction pathway. RBS analysis revealed that Ti is present only on the surface of hydrophilic and moderately hydrophobic polymer films, whereas it was found diffused through the entire thickness of the poly(styrene) films. The reaction pathways of hydrophilic and hydrophobic polymers with HCI4 are different because TiCl is hydrolysed by the surface water at the hydrophilic polymer surfaces to form an etch resistant T1O2 layer. Lack of such surface water in hydrophobic polymers explains the absence of a surface TiC>2 layer and the poor etching selectivities. 

Keeping in mind these factors and the fact that for polymerizations of this type the absence of side reactions, monomer purity and solvent dryness are extremely critical, poly(amic acid) synthesis should be readily accomplished. As it turns out, poly(amic acid) formation is actually a very complex situation and involves some very unique features. As illustrated in Scheme 7, five additional potential reaction pathways besides the propagation reaction are possible. To... 

Scheme 2. Reaction pathway of the formation of poly-alumazane until the sublimation stage.

A series of additional experiments was performed with a Ag(poly) foil [rather than a Au(poly)] foil to examine in more detail the nature of the reaction products of d6-PC with metallic Li, and possible substrate effects. According to data compiled in the literature (Table 3), all of these fragments, except mle = 4, are consistent with, albeit not unique to, ethylene oxide, e.g., acetaldehyde. No features could be identified for mle = 32 and 64, indicating that propylene oxide, if produced, yields signals too small to be detected. Furthermore, no differences were found between the peak shapes and temperatures obtained for these experiments and those observed using Au(poly) hence, the reaction pathway does not seem to be affected by the nature of the substrate. Based on the behavior found for BuOLi, for which the series of high temperature peaks are found in the range... 

The TPD of a BuOH(20 L)/Li(17 ML)/Au(poly) surface, prepared by condensing ultrapurified BuOH on a Li/Au(poly) surface kept at 120 K, revealed, in addition to the features characteristic of bulk BuOH at 200 K, peaks for mle = 57 (curve a), 44 (curve b), 43 (curve c) and 2 (curve d), centered at 580 K (see Figure 27). Also noteworthy is the presence of a second mle = 2 peak at 435 K. A reaction pathway consistent with these data involves the dehydrogenation of BuOH to form the corresponding lithium butoxide (BuOLi) and lithium hydride, which at a sufficiently high temperature undergoes thermal decomposition to yield elemental Li and dihydrogen ... 

The general consensus is that mesoporous silica materials synthesized using surfactant templates can form by two distinct yet related reaction pathways. The first involves the hydrolytic poly-condensation of a silicatropic mesophase while the second works through co-assembly of silicate and surfactant micellar building blocks. For ionic surfactants, cooperative-assembly with silicate precursors is the result of charge density and geometry matching and multi-dentate... 

The purpose of this work is then to study similar B(CgFj)3-catalyzed poly condensation of hydrido and methoxy functionalized silanes and siloxanes in solution, in a view to prepare hybrid silicones (see general reaction pathway in Scheme 1). We considered three routes, first a model reaction to prepare PDMS and two others to synthesize different hybrid silicones, starting from hydrido and methoxy functionalized bricks. 

A multistep reaction pathway leads to polymers 43 and 44 with phosphatidylcholine moieties in the main chain and long alkyl groups in the side chain [122]. These polymers exhibit thermotropic liquid-crystalline behavior. Polyamides 45 were obtained by interfacial polycondensation they are insoluble in any normal solvent [123]. Poly-MPC capped with cholesteryl moieties at one or both polymer ends was prepared by the radical polymerization of MFC initiated with 4,4 -azobis[(3-cholesteryl)-4-cyanopentanoate] in the presence of a chain transfer agent [124]. The self-organization of these polymers was analyzed with fluorescence and NMR measurements. 

Poly( 1,2,4-triazole)s (PT)s are heterocyclic polymers, which were first synthesized by the reaction of bistetrazoles and a bisimidoyl chloride. Meanwhile, several different reaction pathways have been developed to prepare these polymers. ... 

The deposition of Cr on two fluorinated poly(aryl ether) (rPAE) polymers has been investigated with x-ray photoelectron spectroscopy. Fluorine moieties were observed to be highly reactive towards the deposited Cr. Differences in polymeric fluorine chemistry (aliphatic vs. aromatic) did not affect the reaction pathway or the final reaction products. Interfacial deposition products form in a step-wise fashion dependent upon sietal coverage. A model ie proposed whereby the formation of reaction products is initiated by electron transfer from the metal to tha polymer followed by the formation of Cr-fluorldes and finally Cr-carbldes prior to the formation of a continuous unreacted metal overlayer. 

The Poly-Br02 species so formed can decompose following two different reaction pathways ... 

Unexpected reaction products are also often produced by neighboring group participation. For example, poly(methacryloyl chloride) does not follow the normal reaction pathway in the Arndt-Eistert reaction for diazoketone production. Instead, an intermediate )3-ketoketene ring is formed, which then hydrolyzes with decarboxylation to cyclic ketone units... 

In two-step polymerization, initially the polyamic acid is formed from an equimolar mixture of dianhydride and diamine in a polar aprotic solvent such as A,A-dimethylacetamide (DMAc) or A,A-dimeth-ylformamide (DMF). The reaction pathway for the formation of poly(amic acid) involving intermediates is presented in Scheme 3.2. The reaction mechanism involves nucleophilic attack of the amino group to the electrophilic carbonyl carbon of the anhydride group. This opens the anhydride ring to form an amic acid group. Formation of the poly(amic acid) is an equilibration reaction in which the forward reaction... 

Scheme 3.2 Reaction pathway in poly(amic acid)...

The reaction pathways of the DoM reaction promoted by poly(amido)cadmate were found to be different from those previously noted for amidozincates (Scheme 27.17) [69]. 

The oxidative coupling of catechol proceeded in the presence of a peroxidase catalyst [11], during which an unstable o-quinone intermediate may be formed, followed by complicated reaction pathways to give poly(catechol). 

Scheme 30. Two possible reaction pathways for the formation of the main volatile pyrolysis products of poly(epichlorohydrin-co-ethylene oxide)...

PLA can be obtained in two ways through direct polycondensation of the hydroxy acid or by ROP of cyclic lactide monomer. The different reaction pathways to PLA are depicted in Scheme 6.3. Different nomenclatures of polymers obtained by the different routes are often observed in the literature those obtained from lactic acid by direct polycondensation are referred to as poly (lactic acid), while those obtained from lactide monomer by ROP are referred to as poly (lactide). The general abbreviation used in both cases is PLA. 

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