Electron‐transfer polymers. XXIX. Copolymerizability of vinylhydroquinone derivatives

Abstract

SynopsisTen viriylhydroquinone and one vinyl resorcinol derivatives are compared, particularly with respect to NMR spectra and copolymerizability with styrene. They are vinylhydroquinone dimethyl ether (I), viriyl-O,O'-bis(l-ethoxyethyl)hydroquhone (11), vinylhydroquinone di(2-penty1)ether (111), 4-vinyl resorcinol bkmethoxymethyl ether (IV), 2-vinyl-5-methylhydroquinone dimethyl ether (V), 2-vinyl-5methyl-O,0'-bis( 1-ethoxyethy1)hydroquinone (VI), 2-vinyl+methylhydroquinone dimethyl ether (VII), 2-vinyl-Merl-butylhydroquinone dimethyl ether (JqII), %vinyl-5-chlorohydroquinone dimethyl ether (IX), %vinyl-3,6-dirnethylhydroquinone dimethyl ether (X), and 2vinyl-3,5,6-trimethylhydroquinone dimethyl ether (XI). All the vinyl protons have almost the same coupling constants. Though subtle distinctions are found among all the spectra, they can in general be put into two groups on the basis of the chemical shifts.Let the hydrogen on carbon-1 of the vinyl group be A, the hydrogen cis to A be B the hydrogen trans to A be C, then in the first group, (I) through (IX), the chemical shifts ( 7 ) are (A) 3.02 =t 0.08, (C) 4.41 f 0.05, and (B) 4.87 f 0.07, and in the second group, (X) and (XI), they are (A) 3.30 f 0.03, (C) 4.49 f 0.01, and (B) 4.59 f 0.03.It is supposed that in (X) and (XI) the vinyl group is out of the plane of the ring, because of the two ortho substituents, and this conformation is reflected in the NMR data. Ultraviolet spectra are consonant with this interpretation, since the Xmsr of (X) and (XI) correspond closely with those of nonvinyl reference compounds, while those of (11), (V), and (VIII) are shifted to longer wavelengths. , When these compounds are copolymerized separately with styrene, the behaviors are clsssifiable into the following three groups, where r1 and rz are monomer reactivity ratios with styrene the firat monomer: (i) rl < 1 and rz < 1 for compounds (11) and (111) and the reference compound 0,O'dibenzoylvinylhydroquinone, ( i i ) rl < 1 and rz > 1 for compounds (I), (V), (VII), (VIII), (IX), and (iii) rl > 1 and rz = 0 for compounds (X) and (XI). These behaviors are correlated with the effect of electronegativity of groups on the stability of the radical at the growing end of the chain and with the simultaneous effects of steric hindrance. This paper reports a further step1q2 toward the synthesis of polymers in which redox functional groups are spaced out along polymer chains. When fully oxidized and fully reduced polyvinylhydroquinone redox polymers are mixed in solution, a sequence of changes takes place that reflects the exchange of electrons and protons between the functional groups.'*a These changes are indicated by spectral changes of the charge-transfer type that serve as internal indicators of the interactions and are a function of the jstramolecular distance between the redox groups.The observed 2729