Study of chain sequence in the controlled radical telomerization of vinyl acetate with Co(acac)2 catalyst in bulk

Abstract

Kinetics of radical telomerization of vinyl acetate (VAc) with CDCl 3 as telogen in the presence of AIBN initiator and ZnCl 2 and Co(acac) 2 as catalysis in bulk and solution telomerization was studied through 1 HNMR and GPC. The telomerization of vinyl acetate in chloroform has indicated a random chain sequence with free radical initiators. Co(acac) 2 catalyst, in this reaction controls the tacticity of the telomer chain. The narrower molecular weight distribution of telomer with its higher yield is predominantly syndiotactic. 1 HNMR study of the microstructure of the telomers revealed that the sequential arrangement of CH 2 and CH groups in telomer is controlled in bulk telomerization by Co(acac) 2 catalyst.

Synthesis and Characterization of PDMS Based Triblock and Pentablock Copolymers

“…3.6 at −59°C [6,10]. PVAc and PSt segments exhibited T g values of 40 and 105°C [9,12,13], respectively for the The linear fit indicated that the concentration of propagating radical species is constant and radical termination reactions are not significant over time scale of the reaction. It was found that the molecular weights increase almost linearly with conversion, indicating that the number of chains was constant and the chain transfer reactions were rather negligible [16][17][18].…”

“…3.5. All signals of the 1 H-NMR spectra were assigned to their corresponding monomers and it can be declared that the synthesis of pentablock copolymers have proceeded successfully [12,13]. The 1 H-NMR of pentablock showed a signal at 0.0-0.2 ppm associated with CH 3 -Si methyl protons of PDMS along with the signals at 2.1-2.3 and 6.6-7.1 ppm corresponded to OCOCH 3 group from the PVAc segment and PSt segment respectively.…”

“…The area ratio of 6H signal from PSi to that of vinyl acetate showed that the ratio of sequence lengths of PVAc with respect to PDMS was found as X = (A/6)/(A*/6) = 2.14 (A* and A represent areas for the protons of methyl groups of -Si(CH 3 ) 2 O and vinyl protons, respectively). It was possible to synthesize the PDMS-based triblock copolymers via ATRP from vinyl acetate in the presence of OH-PDMS-OH macroinitiator [10][11][12]. DSC thermograms of PVAc-b-PDMS-b-PVAc initiated with Br-PDMS-Br at 60°C for PDMS-based triblock copolymers at the range of −150 to 150°C are depicted in Fig.…”

“…The 1 H-NMR of pentablock showed a signal at 0.0-0.2 ppm associated with CH 3 -Si methyl protons of PDMS along with the signals at 2.1-2.3 and 6.6-7.1 ppm corresponded to OCOCH 3 group from the PVAc segment and PSt segment respectively. Therefore, it is possible to synthesize the PDMS-based pentablock [12,13].…”

“…Therefore, it is possible to synthesize the PDMS-based pentablock copolymers via ATRP of monomers such as vinyl acetate and styrene in the presence of OH-PDMS-OH macroinitiator [12,13]. DSC thermograms of PDMS-based block copolymers are depicted in Fig.…”