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Kinetic Investigation of the Free-radical Cross-linking Copolymerization of Methyl- Methacrylate and Ethylene Glycol Dimethacrylate by Using Bifunctional Initiator
| Content Provider | Semantic Scholar |
|---|---|
| Author | Naghash, Hamid Javaherian Malakpour, S. H. |
| Copyright Year | 2004 |
| Abstract | methyl methacrylate (MMA) 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)-bis benzoin (ACPB). Conversion of monomer and pendant vinyl groups and the size of the pre-gel 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 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 pre-gel polymers change from monomodal to bimodal distributions as polymerization proceeds. This finding confirms the coagulationtype gelation mechanism of compact primary particles and indicates the polydispersity shape of the pre-gel polymers. Virtually we observed the same kinetic behaviour in the MMA-EGDM polymer gel systems by bifunctional initiator the same way we had found before with photo and thermal initiators. Hamid Javaherian Naghash* and Shadpour Mallakpour |
| Starting Page | 287 |
| Ending Page | 295 |
| Page Count | 9 |
| File Format | PDF HTM / HTML |
| Volume Number | 13 |
| Alternate Webpage(s) | http://journal.ippi.ac.ir/manuscripts/ipjE04130406.pdf |
| Alternate Webpage(s) | https://www.sid.ir/FileServer/JE/81320040406.pdf |
| Alternate Webpage(s) | https://www.sid.ir/FileServer/JE/81320040406 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
