P-Fluorostyrene

A theoretical investigation of the use of NMR lineshape second moments in determining elastomer chain configurations has been undertaken. Monte Carlo chains have been generated by computer using a modified rotational isomeric state (RIS) theory in which parameters have been included which simulate bulk uniaxial deformation. The behavior of the model for a hypothetical poly(methylene) system and for a real poly(p-fluorostyrene) system has been examined. Excluded volume effects are described. Initial experimental approaches are discussed. 

The algorithm also incorporates tacticity control for vinyl chains. The random number generator is used to choose between d- and l-versions of the transformation matrix. A single parameter controls the relative probability of d- and l-residues. The poly(p-fluorostyrene) results presented here are for atactic (stereochemically irregular) chains. 

A preferable system is poly(p-fluorostyrene) doped into poly(styrene). Since rotations about the 1,4 phenyl axis do not alter the position of the fluorine, the F spin may be regarded as being at the end of a long "bond" to the backbone carbon. In standard RIS theory, this polymer would be treated with dyad statistical weights to automatically take into account conformations of the vinyl monomer unit which are excluded on steric grounds. We have found it more convenient to retain the monad statistical weight structure employed for the poly(methylene) calculations. The calculations reproduce the experimental unperturbed dimensions quite well when a reasonable set of hard sphere exclusion distances is employed. 

Figure 5. ORTEP computer plot showing the positions of the fluorine atoms of the first 50 backbone carbons of a poly(p-fluorostyrene) chain. The excluded volumes used in the calculation keep the fluorines well separated.

Figure 7. Average values of for poly(p-fluorostyrene) chains of 200 backbone atoms, 100 chains per point. In this calculation, the fluorines are at their correct locations on the sidegroups.

N-Methylpyrrolidinone 2-Pyrrolidinone, 1-methyl- (8,9) (872-50-4) p-Fluorostyrene Styrene, p-fluoro- (8) Benzene, 1-ethenyl-4-fluoro- (9) (405-99-2)... 

When DISN reacts with electron-rich styrenes such as p-methoxystyrene, good yields of reduced pyrazines 117, often accompanied by their oxidized forms, are obtained. However, reaction with electron-deficient styrenes like p-fluorostyrene give the 2-amino-3-(2-arylaziridin-l-yl)maleonitriles (118) (72JA3242 84JOC813). 

Fig. 5. Miscibility of poly(2,6-dimethyl phenylene oxide) (PPO) and random copolymers of styrene and o-bromostyrene (7), p-fluorostyrene (2), p-bromostyrene (i), o-chlorostyrene (4), p-chlorostyrene (5), and o-fluorostyrene (<5) for 50/50 blends. Miscibility occurs to the left of the curves (after Ref. [29])...

PPO and poly(o-fluorostyrene-rnn-p-fluorostyrene) one phase region between 7 and 42 mol% p-fluorostyrene [29]... 

REDOR was also applied to examine the structure and dynamics of interfaces of heterogeneous polymer blends. A heterogeneous blend was prepared from [carbonyl- C]polycarbonate and poly(p-fluorostyren-co-styrene) copolymer of p-fluorostylene. The blend was formed by coprecipitation from chloroform into methanol. A fluorine dephased REDOR signal indicates that the 1 polycarbonate chain in 20 exists at the interface, suggesting that the polycarbonate phase is embedded in a continuous polystyrene matrix which is 200 A thick or 400 A in diameter [54],... 

Fig. 10.26. Carbon-observe, fluorine-dephase REDOR NMR spectra of a heterogeneous blend of [carbonyl- CJpolycarbonate and poly(p-fluorostyrene-co-styrene) as a function of the number of rotor cycles of 5 kHz magic-angle spinning. The natural-abundance background has been subtracted from both the top and bottom sets of spectra. The REDOR difference (top) arises exclusively from the polycarbonate carbons at the interface. (Reprinted with permission from Ref. [153]. 1995 American Chemical Society, Washington, DC.)...

Hydrofluorination of alkynylarenes delivers (Z)-p-fluorostyrenes on treatment with 3HF Et3N and catalytic amounts of the Au complex. ... 

Abbreviations for Table 2.19 PHMA - poly-n-hexyl methacrylate, STVPh - polystyrene-co-vinylphenol, PFSt - poly(o-fluorostyrene-co-p-fluorostyrene), P(S-co-BrS) - poly(styrene-co-4-bromostyrene), N-TPI - new thermoplastic polyimide , PPrA - poly-n-propyl acrylate, PPeA - poly-n-pentyl acrylate,... 

For instance, the reaction of EtaSiH and 2 equiv. of p-methoxystyrene in toluene with 1.0 mol% of 16a afforded at 100°C within 6 h the dehydrogenative silylation product ( )-l-(p-methoxystyryl)-2-(triethyl-silyl)ethylene in 95% yield. The reaction is of high selectivity that neither (Z)-isomers, nor branched dehydrogenative silylation products were seen. Less hydridic silanes, such as triphenylsilane, were less efficient than for instance EtsSiH. Other substituted styrenes such as p-methyl, p-chloro-, and p-fluorostyrene also afforded the corresponding tran -vinylsilanes in high yields and selectivities (up to 98%). In the case of aliphatic alkenes, such as -octene, allyltriethoxysilane, vinylcyclohexane, and ethylene, dehydrogenative silylations were still preferred, but showed less E/Z selectivity. Cyclic olefins, such as cyclooctene, furnished low conversions under the same reaction crmditions. The results are summarized in Scheme 19. 

Ruorostyrene-co-p-styrene o-Ruorostyrene-co-p-styrene Single Tg I and n had 10 and 23 mol% p-fluorostyrene, respectively Oudhuis et al. (1993)... 

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