Paper Information

Journal:   IRANIAN POLYMER JOURNAL (ENGLISH)   July-August 2004 , Volume 13 , Number 4; Page(s) 287 To 295.
 
Paper: 

KINETIC INVESTIGATION OF THE FREE-RADICAL CROSS-LINKING COPOLYMERIZATION OF METHYL- METHACRYLATE AND ETHYLENE GLYCOL DIMETHACRYLATE BY USING BIFUNCTIONAL INITIATOR

 
 
Author(s):  JAVAHERIAN NAGHASH H.*, MALAKPOUR SH.
 
* Department of Chemistry, Shahreza Islamic Azad University, Shahreza-84145-311 Isfahan, I.R. Iran
 
Abstract: 

Both photo-and thermal initiated free-radical cross-linking copolymerization of methylmethacrylate and ethylene glycol dimethacrylate (EGDM) have been investigated in toluene at a monomer concentration of 3.5 molar and at 60°C and 27°C for azo and benzoin groups, respectively. The bifunctional initiator used was 4,4'-azo-bis-(4-cyanopentanoyl)-bisbenzoin (ACPB). Conversion of monomer and pendant vinyl groups and the size of the pregel polymers were measured as a function of the reaction time up to the onset of macrogelation. Approximately 97% of the pendant vinyl groups were found to be consumed by cyclization reactions. The fraction of units in cycles is independent of the EGDM concentration. As a result of the cyclization reactions , the accessibility of the radical centres and pendant vinyl groups for other polymer molecules is strongly reduced. Consequently, both termination and cross-linking reactions are controlled by the segmental diffusion of the polymer radicals. Calculations indicate a 1-2 orders of magnitude decrease in the average reactivity of pendant vinyls for intermolecular reactions compared to the monomeric vinyls. This drastic decrease in pendant reactivity is mainly responsible for the delay in the gel point. Contrary to gelation theories, the size distribution curves of the pregel polymers change from monomodal to bimodal distributions as polymerization proceeds. This finding confirms the coagulation-type gelation mechanism of compact primary particles and indicates the polydispersity shape of the pregel polymers. Virtually we observed the same kinetic behaviour in the MMA-EGDM polymer gel systems by bifunctional initiator, as the same way we had found before with photo and thermal initiators.

 
Keyword(s): FREE RADICAL CROSS-LINKING COPOLYMERIZATION, BIFUNCTIONAL INITIATOR, METHYL METHACRYLATE, ETHYLENE GLYCOL DIMETHACRYLATE
 
References: 
  • ندارد
 
  pdf-File tarjomyar Persian Abstract Yearly Visit 96
 
Latest on Blog
Enter SID Blog