Suspension polymerization of vinyl chloride at low temperature with the use of monomer‐soluble redox initiators

Abstract

Suspension polymerization of vinyl chloride was carried out at temperatures of ‐30° to +30°C. with the use of a monomer‐soluble oxidation‐reduction initiator system. A typical initiator system was composed of lauroyl peroxide and ferrous n‐caproate. The effects of temperature, molar ratio of peroxide to reducing agent, and total concentration of initiator upon the rate and degree of polymerization were observed. The activation energy of the overall rate of polymerization was 6.5 kcal./mole. Experimental evidence which may serve to elucidate the mechanism of the redox reaction in the nonemulsified system is discussed.

Solving the Problem of Bis(acetylacetonato)cobalt(II)-Mediated Radical Polymerization (CMRP) of Acrylic Esters

“…39 The LPO/Co(acac) 2 redox initiating system most probably proceeds similarly to conventional redox systems, 38 since diacyl peroxides (e.g., LPO) are known to initiate radical polymerizations after reaction with various types of reducing agents, such as Co(II) salts. [40][41][42] This CMRP redox system was thus investigated for the controlled polymerization of acrylates. At first, a mixture of nBA and VAc (50/50) was polymerized from LPO in presence of Co(acac) 2 ([LPO]/[Co(acac) 2 ] = 1/3) at 0 °C.…”

“…Although the initiation at 30 °C suffered from a low efficiency (0.1 < f < 0.2), the polymerization was controlled, and the resulting PVAc had a reasonably low polydispersity ( M w / M n = 1.3) . The LPO/Co(acac) 2 redox initiating system most probably proceeds similarly to conventional redox systems, since diacyl peroxides (e.g., LPO) are known to initiate radical polymerizations after reaction with various types of reducing agents, such as Co(II) salts. − …”

Ferrocene/ferrocenium redox shuttling: Peroxide decomposition catalysis applied to vinyl monomers polymerization under suspension conditions

“…As early examples, the use of AA in combination with tert-butyl perbenzoate has been described, which allows the homogeneous polymerization of vinyl acetate in alcoholic medium [6] or that of 6-O-palmitoyl-L-ascorbic acid (PAA) in bulk or suspension polymerization of vinyl chloride with methyl ethyl ketone peroxide [7] or t-butyl peroxyoctoate [8]. Among the inorganic reductants, iron(II) carboxylates have been shown in the early sixties to be efficient for VCM and vinyl acetate (VAc) polymerizations under suspension conditions [9]. In such reactions, the enhancement of the initiation process is occurring via a monoelectronic transfer reaction between the peroxide and the iron(II) species, leading to the cleavage of the O-O bond into a radical and an anion together with the formation of the oxidized iron(III) derivative according to the well-known Haber-Weiss reaction (scheme 1) [10].…”

A mononuclear cobalt(iii) carboxylate complex with a fully O-based coordination sphere: CoIII–O bond homolysis and controlled radical polymerisation from [Co(acac)2(O2CPh)]

“…The generally accepted radical initiation mechanism 47,48 for the combination of a peroxide and a reducing metal complex is as illustrated in eqn ( 1) and ( 2) (Mt = generic metal, L/ = coordination sphere). However, none of the above-mentioned investigations, nor other ones dealing with Co II /peroxide-initiated free radical polymerisations, [49][50][51][52][53][54] could elucidate the nature of the Co III species produced by reaction (1).…”