12 Emulsion Redox Copolymerization of Vinyl Ferrocene F. LOUIS FLOYD
Downloaded by NORTH CAROLINA STATE UNIV on December 27, 2012 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/bk-1976-0024.ch012
Glidden-Durkee Div., SCM Corp., Strongsville, Ohio 44136
Only recently has the field of metallocenes become of inter est to polymer chemists. Ferrocene (I), being the oldest, most readily available, and best characterized of the class, was the logical choice for initial studies. Ferrocene and vinyl ferrocene (II) can be thought of as analogs of benzene and styrene, respec tively, undergoing many of the same kinds of reactions, including polymerization of vinyl ferrocene. Two excellent reviews of the
use of metallocenes in general, and ferrocene in particular, in polymers are those of Pittman(1), and Neuse(2). Poly(vinyl ferrocene) was first prepared by Arimoto and Haven in 1955, (3) a process for which was patented in 1958 (4). Vinyl ferrocene was found to be much less reactive than styrene, but still readily polymerizable with azo initiators. Peroxide initiators were, in general, not effective, causing the ferrocene nucleus to oxidize instead (1). Although there are numerous references to the emulsion poly merization of vinyl ferrocene, they a l l appear to emanate from a single source (4). These workers polymerized vinyl ferrocene alone, and with styrene, methyl methacrylate, and chloroprene. No characterization was reported other than elemental analysis. The molding temperatures reported (150 - 200°C) correspond to the Tg range indicated by Pittman (1) for similar copolymers. The initia tion system was preferably azobisisobutyronitrile, although potassium persulfate was also used. Organic peroxides were contraindicated, due to oxidation problems with the ferrocene moiety. Because of the reported property advantages of the ferrocene moiety i n polymers, t h i s work was undertaken to a s c e r t a i n i f v i n y l ferrocene could be redox copolymerized with other common monomers without serious problems.
188
In Emulsion Polymerization; Piirma, I., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1976.
12.
FLOYD
Emulsion
Redox Copolymerization
of Vinyl
Ferrocene
189
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Experimental The current work was concerned with the emulsion copolymeri z a t i o n of v i n y l ferrocene with b u t y l a c r y l a t e , styrene, and m e t h a c r y l i c a c i d to y i e l d a film-forming composition of Tg~0~5°C. Using the l i t e r a t u r e recommendations, i n i t i a l work was centered on azo i n i t i a t o r s due to the c l a i m that the peroxides i n redox systems o x i d i z e d the v i n y l ferrocene r a t h e r than polymerized it. I n i t i a l experiments r e s u l t e d i n slow r e a c t i o n s and poor con v e r s i o n s , even a f t e r 8 - 1 2 hours r e a c t i o n time. Reasoning that redox systems might work i f the reducing agent were kept i n excess i n the r e a c t i o n f l a s k , a tBHP/Formopon c a t a l y s t system was examined. This i n i t i a t o r system r e s u l t e d i n complete conversion w i t h i n 2 - 3 hours and served as a prototype r e c i p e i n a l l sub sequent work. 1
Example: Synthesis of Latex Containing 5% V i n y l
Ferrocene
The f o l l o w i n g i n g r e d i e n t s were employed i n the synethesis of a conventional emulsion polymer: Part A:
1312. gm d e i o n i z e d water 49.6gm A e r o s o l AY-65 (65%) 16. gm Formopon^ 5
Part B:
856. 832. 32. 80.
gm gm gm gm
styrene butyl acrylate methacrylic acid v i n y l ferrocene
Part C:
720. gm d e i o n i z e d water 22.4gm T r i t o n X-405 (70%) 8
Part D:
9
22.4gm tBHP(70%) 400. gm d e i o n i z e d water Part A i s charged to a 3-neck, morton-style, 5 - l i t e r f l a s k and purged with n i t r o g e n while heating to 60+ 1°C. Part Β i s e m u l s i f i e d i n t o Part C by slow a d d i t i o n while s t i r r i n g on a h i g h speed bench s t i r r e r . This monomer emulsion (ME) i s l i k e w i s e purged with n i t r o g e n as i s P a r t D. 10% of ME i s added to the r e a c t i o n f l a s k a f t e r 30 minutes' purging f o r a l l p a r t s and e q u i l i b r a t e d by s t i r r i n g f o r 5 minutes. 10% Part D i s added to i n i t i a t e polymerization, and ME s t a r t e d on gradual a d d i t i o n such that t o t a l a d d i t i o n time i s 2 hours. Part D i s added i n 10% a l i q u o t s during s a i d time to maintain the exotherm. The r e a c t i o n i s maintained at a minimum of 60°C, with the exotherm allowed to run i t s course (
