Monomers cyano

Cyano monomers are olefin compounds bearing one or two cyano groups (Scheme 20.2). 

As VCN is difficult to synthesize, other polymers based on commercially available cyano monomer such as acrylonitrile (AN) have also been used. 

Poly(Mc-co-MATRIF) Copolymers (M Stands for AN, MAN, or MVCN) Poly(Mc-co-MATRIF) copolymers were synthesized from equimolar amounts of cyano monomers and MATRIF initiated by AIBN (Scheme 20.5) [73]. The yields of the copolymerizations were ranging between 40% and 60%. 

Values of the percentages of incorporated cyano monomer calculated from arithmetic mean of nitrogen, oxygen, and fluorine percentages. 

TABLE 20.2 Reactivity Ratios of Cyano Monomers (r ) and MATRIF (rj) and the Values of the Product (r X Calculated from the Alfrey-Price Parameters (T = 80° C) [73]... 

The structure of this copolymer was characterized by IR, and NMR, GPC, DSC, and TGA. The composition of the poly(TSE-co-4FST) copolymer was calculated from nitrogen analysis (%N = 7.22%), the molar percentage of cyano monomer (TSE) was closed to 38%. The molecular weight calculated from SEC using polystyrenes as standards was around 8000 g/mol. 

SCHEME 20.8 Synthesis of PVDF-fc-PMcK block copolymers by ITP of cyano monomers Mcn [89]. 

As expected, as the refractive indexes of fluorinated polymers are very low, SEC analysis displayed negative signal assigned to PVDF block response, whereas, the final PVDF-fe-PM(2N block copolymers were identified by positive signals. The values of A/jj (Table 20.6) show that the reactivity of cyano monomers toward the VDF macroradicals can be classified in the following decreasing order AN > MAN > VCN. 

This chapter summarizes (i) the synthesis of fluoro and cyano monomers, (ii) the preparation and characterization of their respective homopolymer and copolymers, and (iii) the study of the dielectric behavior of the resulting cyanofluoropolymers. 

Cyano monomers such as MVCN, VCN, and TSE were synthesized. Copolymers based on MATRIF were produced by radical copolymerization with AN, MAN, MVCN, and VCN. Kinetics of radical copolymerization of AN with ATRIF has... 

Vinylpyridine (23) came into prominence around 1950 as a component of latex. Butadiene and styrene monomers were used with (23) to make a terpolymer that bonded fabric cords to the mbber matrix of automobile tires (25). More recendy, the abiUty of (23) to act as a Michael acceptor has been exploited in a synthesis of 4-dimethylaminopyridine (DMAP) (24) (26). The sequence consists of a Michael addition of (23) to 4-cyanopyridine (15), replacement of the 4-cyano substituent by dimethylamine (taking advantage of the activation of the cyano group by quatemization of the pyridine ring), and base-cataly2ed dequatemization (retro Michael addition). 4-r)imethyl aminopyri dine is one of the most effective acylation catalysts known (27). 

In the absence of heteroatom containing substituents (e.g. halo-, cyano-), at or conjugated with the radical center, carbon-centered radicals have nucleophilic character. Thus, simple alkyl radicals generally show higher reactivity toward electron-deficient monomers (eg. acrylic monomers) than towards electron-rich monomers (e.g, VAc, S) - Table 3.6. 

However, there are also examples of addition across a strained carbon-carbon single bond, as occurs with bicyclobutane1 and derivatives (Scheme 4.21, Scheme 4.22).180,181 Interestingly, l-cyano-2,2,4,4-letramethylbieylobulane (31) is reported to provide a polykctcniminc (Scheme 4.22).183 This is the only known examples of a a-cyanoalkyl radical adding monomer via nitrogen. 

X indicates a small substituent, which may be an atom such as hydrogen (H) or chlorine (Cl) or it may he a group such as methyl (CH3), cyano (CN), carhoxyl (COOH), carbomethoxy (COOCH3), etc. The growing chain is terminated by collision with another chain or other radical source or by one of several other mechanisms. The number of monomer units in the polymer chain is the degree of polymerization, abbreviated DP. If the degree of polymerization is very low, the product is sometimes referred to as an oligomer. 

Horhold et al. and Lenz et al. [94,95]. The polycondensation provides the cyano-PPVs as insoluble, intractable powders. Holmes et al. [96], and later on Rikken et al. [97], described a new family of soluble, well-characterized 2,5-dialkyl- and 2,5-dialkoxy-substituted poly(pflrfl-phenylene-cyanovinylene)s (74b) synthesized by Knoevenagel condensation-polymerization of the corresponding alkyl-or alkoxy-substituted aromatic monomers. Careful control of the reaction conditions (tetra-n-butyl ammonium hydroxide as base) is required to avoid Michael-type addition. 

In the 2,5-DSP(a) and P2VB crystals, the directions of three axes of the polymer coincide with those of the monomer whereas a different type of relative orientation is seen in diphenyl- and diethyl 1,4-phenylene diacrylates (3 OPh and 3 OEt), and dipropyl 1,4-(2-cyano)-phenylene diacrylate (4 OPr). 

The synthesis of the oligomers involved the known reaction of isocyanates and cyanamide (Nl CN). For example, N-cyano-N -phenyl urea has been synthesized from phenyl isocyanate and an aqueous alkaline solution of cyanamide in high yield.(3) Recently, similar reactions were used to prepare various di-N-cyanourea compounds from diisocyanates. ( 1) These monomers were also synthesized directly by reacting diisocyanates with cyanamide at melt temperatures. 

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