Low concentration limitations of the catalyst and conventional free radical polymerization are investigated in the system of initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) of butyl methacrylate (BMA), in which 2,2-azobisisobutyronitrile (AIBN) is used as a reducing agent, pentamethyldiethylenetriamine (PMDETA) as a ligand, copper bromide (CuBr2) as a catalyst and ethyl 2-bromoisobutyrate (EBiB) as an initiator. Results show that conventional radical polymerization happens in the early stage of the ICAR ATRP of BMA when the amounts of AIBN are 3~25 times of the catalyst. And with the increase of the conversion, the BMA polymerization solely conducts the controlled radical polymerization (CRP). The low concentration limitations (based on monomer) of the catalyst required in ICAR ATRP of BMA with good controllability are found to be closely related to the molar ratio of initiator to catalyst, which is determined by the stability of the catalyst/ligand complex. The smaller molar ratio of initiator to catalyst allows lower concentration limitations of the catalyst. 相似文献
Kinetic modeling is used to better understand and optimize initiators for continuous activator regeneration atom‐transfer radical polymerization (ICAR ATRP). The polymerization conditions are adjusted as a function of the ATRP catalyst reactivity for two monomers, methyl methacrylate and styrene. In order to prepare a well‐controlled ICAR ATRP process with a low catalyst amount (ppm level), a sufficiently low initial concentration of conventional radical initiator relative to the initial ATRP initiator is required. In some cases, stepwise addition of a conventional radical initiator is needed to reach high conversion. Under such conditions, the equilibrium of the activation/deactivation process for macromolecular species can be established already at low conversion.
The kinetics of free radical polymerization of methylacrylate (MA) was investigated using benzyltributylammonium chloride (BTBAC) as phase transfer catalyst and potassium peroxydisulfate as initiator at aconstant temperature, 60°C, in an inert atmosphere under unstirred condition. The effect of concentrations of the monomer, initiator and the catalyst on polymerization was discussed and a mechanism of polymerization has been proposed. The order with respect to the monomer, initiator, and phase transfer catalyst was found to be 2, 0.5, and 0.5, respectively. 相似文献
Living methacrylate polymers are obtained at room temperature and above by initiation with ketene silyl acetals in the presence of a soluble bifluoride catalyst. During the polymerization, a trialkylsilyl group is transferred from the living chain end to incoming monomer. The new procedure has thus been named group transfer polymerization (GTP). Monodisperse polymers with predetermined molecular weights as high as 100,000 can be obtained by adjusting the monomer/initiator ratio. Telechelic poly(methyl methacrylate) with hydroxy or carboxy ends can be obtained by using an initiator containing a protected hydroxy or carboxy group and coupling the resulting living polymer. 相似文献