A number of nitroxide adducts and N-acyloxytrialkylammonium salts were prepared, isolated, characterized and evaluated as initiators for the controlled and living free radical polymerization of methacrylate and dimethacrylate monomers under mildly thermal and photochemical conditions. The initiators and polymerization methods that were developed could potentially be used for improving resins employed in dental applications. Using very easy synthesis strategies, the following nitroxide initiators were prepared in high purity, isolated and characterized: 1-Benzoylperoxy-2,2,6,6-tetramethyl-piperidine (BPO/TEMPO), 1-(2'-Cyano-2'-propoxy)-2,2,6,6-tetramethylpiperidine (AIBN/TEMPO), 1,1-ditertbutyl-1-(1-methyl-1-cyanoethoxy)-amine (AIBN/DBN), 1,1-ditertbutyl-1-(benzoylperoxy)-amine (BPO/DBN) and 2,2,6,6,-tetramethyl-4-oxo-1-(1-methyl-1-cyanoethoxy)-piperidine (AIBN/4-OXO-TEMPO). Using H2SO4 additive and an improved unimolecular initiation in nitroxide mediated polymerization, living and controlled polymerization of methyl methacrylate (MMA), tri-ethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A dimethacrylate (EBPADMA) were accomplished, for the first time ever for most of the initiators. Linear polymers (PMMA) were produced in high yield (93 %) under mildly thermal conditions (T = 70 oC) and with excellent attributes: (PDI = 1.04-1.26), Mn (87000), Tg (122-128 oC), Td (290-410 oC). Highly crosslinked polymers, poly(TEGDMA) and poly(EBPADMA), were produced in high yield (100 %) with Td (350-400 oC). The initiators were stable for a year and half at 0 oC. Two routes were investigated for the preparation of N-acyloxytrialkylammonium salts. The more efficient of these routes was used to make several novel analogs of the salts. The salts were evaluated for the free radical polymerization of MMA, TEGDMA and EBPADMA under mildly thermal (T = 60 oC) conditions with and without H2SO4 additive. Polymerization rate, yield and polymer attributes all improved upon application of H2SO4 additive. PMMA was produced with excellent attributes (PDI = 1.01-1.06), Mn (96,000-122000), Td (330-385) and Tg (127-134). Highly crosslinked poly(TEGDMA) and poly(EBPADMA) were produced with Td ranges of 300-374 oC and 375-411 oC respectively. / Chemistry
| Identifer | oai:union.ndltd.org:TEMPLE/oai:scholarshare.temple.edu:20.500.12613/3714 |
| Date | January 2008 |
| Creators | Ansong, Omari E |
| Contributors | Wunder, Stephanie L., Varnum, Susan A., Stanley, Robert J., Wei, Yan |
| Publisher | Temple University. Libraries |
| Source Sets | Temple University |
| Language | English |
| Detected Language | English |
| Type | Thesis/Dissertation, Text |
| Format | 153 pages |
| Rights | IN COPYRIGHT- This Rights Statement can be used for an Item that is in copyright. Using this statement implies that the organization making this Item available has determined that the Item is in copyright and either is the rights-holder, has obtained permission from the rights-holder(s) to make their Work(s) available, or makes the Item available under an exception or limitation to copyright (including Fair Use) that entitles it to make the Item available., http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | http://dx.doi.org/10.34944/dspace/3696, Theses and Dissertations |
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