Aqueous emulsion homo- and copolymerization of 1,3-dienes and styrene in the presence of Cp2TiCl2

Abstract

The aqueous emulsion homopolymerizations of 1,3-butadiene and isoprene were investigated using bis-cyclopentadienyl titanium dichloride (Cp 2 TiCl 2) as an active initiator. The copolymerizations of the same monomers with styrene were also performed. Cp 2 TiCl 2 , which has already been used for the production of atactic polystyrene, exhibited low activity in the homopolymerization of conjugated dienes, whereas better performance was obtained in copolymerization reactions. Both of the homopolymers, polybutadiene and polyisoprene, presented similar microstructures. The majority of the polymer chains were formed by 1,4-trans units and, to a lesser extent, by 1,4-cis and 1,2 (3,4 in the case of isoprene) units. All the copolymers presented a statistical distribution with atactic polystyrene sequences and 1,4-trans, 1,4-cis and 1,2 (3,4 in the case of isoprene) diene units. The copolymerization activity values and the percentage of inserted diene units were strictly correlated to the composition of the reaction mixture. The molecular weights of the co-polymers were substantially less than those detected for the styrene homopolymer and similar to those detected for polybutadiene and polyisoprene. Depending on the composition of the copolymer, the glass transition temperatures presented values between those of polystyrene and polydienes.

RAFT solution copolymerization of styrene and 1,3-butadiene and its application as a tool for block copolymer preparation

“…NMR spectra were recorded on an AMX-600 spectrometer (Bruker, Germany) at 25 1C in the indicated deuterated solvents and listed in ppm. The signal corresponding to the residual protons of the deuterated solvent was used as an internal standard for 1 H and 13 C NMR. Signal assignment was performed using 2D NMR techniques: heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond correlation (HMBC), H-H correlation spectroscopy (H-H COSY).…”

“…s, 2H, H11), 1.15 (br. t, 3H, J = 6 Hz, H7mm), 0.96 (s, 3H, H7mr), 0.79 (s, 3H, H7rr); 13 Bd (20.00 g, 370 mmol) was distilled into a pressure stable glass reactor (Bu ¨chiglasuster, Switzerland) pre-cooled at À20 1C under vacuum. Afterwards, the reactor was filled with an inert atmosphere (Ar) up to 0.1 bar overpressure.…”

“…These polymers were chosen as samples prepared in different solvents and with different [CTA]:[Initiator] ratios. At first, their structure and purity were proved by 1 H and 13 C NMR (Fig. 2 and Fig.…”

“…9,10 Moreover, in comparison with anionic polymerization, RAFT is less sensitive to moisture, 11 while compared to emulsion radical polymerization, RAFT offers reduced branching and narrower molecular weight distributions. [12][13][14] Although attempts to produce Bd-based copolymers using several chain transfer agents (CTA) and macro-CTA agents have been carried out via emulsion RAFT polymerization [15][16][17] (for a recent review, see 18 ), or via photo RAFT polymerization in the continuousflow reactor, 19 the studies dedicated to Bd RAFT (co)polymerization in solution are few and far between. As of this writing, the authors are aware of only seven published reports describing the solution RAFT homopolymerization of Bd [20][21][22] and its copolymerization with acrylonitrile.…”