Phthalate plasticizers covalently linked to PVC \u3ci\u3evia\u3c/i\u3e copper-free or copper catalyzed axide-alkyne cycloadditions

Plasticization of PVC was carried out by covalently linking phthalate derivatives via copper-free (thermal) or copper catalyzed azide-alkyne cycloadditions. Di(2-ethylhexyl) phthalate derivatives (DEHP-ether and DEHP-ester) were synthesized and appended to PVC at two different densities. The glass transition temperatures of the modified PVC decreased with increasing content of plasticizer. PVC-DEHP-ether gave lower glass transition temperatures than PVC-DEHP-ester, reflecting the enhanced flexibility of the ether versus ester linker

Synthesis of fluorinated alkoxyamines and alkoxyamine-initiated nitroxide-mediated precipitation polymerizations of styrene in supercritical carbon dioxide

TIPNO (2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide)-alkoxyamine was found to give reasonably controlled/living nitroxide-mediated (NMP) precipitation polymerizations of styrene in supercritical carbon dioxide (scCO(2)). In contrast under the same conditions, the analogous SG1 (N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)nitroxide)-alkoxyamine gave higher rates of polymerization and inferior controlled/living character. The circumvention of the requirement for excess free (nitroxide](0) allowed the study of nitroxide partitioning effects in scCO(2) for three newly synthesized fluorinated alkoxyamines. Two alkoxyamines dissociated into scCO(2)-philic fluorinated TIPNO-nitroxide derivatives, while another contains a similar sized fluorinated "foot". Despite the increased steric bulk about the N-O bond for the novel fluorinated alkoxyamines, all polymerizations proceeded at a similar rate and level of control to the TIPNO system in solution (toluene). PREDICI simulations for the styrene/TIPNO system are used to support extensive partitioning effects observed in scCO(2) for the fluorinated alkoxyamines.Irish Research Council (formerly IRCSET) IUPAC Transnational Call in Polymer Chemistry to F.Aldabbagh. National Science Foundation (NSF CHE-1057927, USA) to R. Braslau.peer-reviewe

Plasticization of PVC: Covalently Linked Plasticizers Using Thermal or Copper-Catalyzed Azide-Alkyne Cycloadditions

One of the most effective approaches to avoid migration of plasticizer from PVC material is to covalently attach the plasticizer to the polymer. In this thesis the plasticizers are attached to PVC using (2+3) azide-alkyne cycloaddition reactions. In the first approach, PVC was modified by covalently linking triazole anologue of the most common phthalate plasticizer di(2-ethylhexyl phthalate) (DEHP). Copper-free azide-alkyne (2+3) cycloaddition reaction of PVC-azide with electron-poor acetylene dicarboxylate is utilized to modify PVC. The glass transition temperature of the modified PVC was lower than the glass transition temperature of the unmodified PVC indicating successful plasticization. The derivatives of DEHP are covalently bonded to PVC using either thermal or copper-catalyzed (2+3) azide-alkyne cycloaddition reaction. Two DEHP derivatives bearing a tether ending with a terminal alkyne were synthesized and covalently bonded to PVC. The derivative with ether-alkyne undergoes cycloaddition with PVC-azide under copper-catalyzed conditions whereas ester-alkyne derivative undergoes Huisgen thermal cycloaddition. The investigation of glass transition temperatures of these modified PVC samples indicate that the ether-alkyne derivative is more efficient in imparting plasticization to PVC compared to ester-alkyne derivative. Although bulk of this thesis work is on the plasticization of PVC, a part of this thesis deals with the synthesis and spin-trapping properties of polymer-supported trifluoromethylated cyclic nitrones for the detection of free radicals on the aerosol particles. Polystyrene tethered with fluorinated nitrone spin-trap is used as a solid phase in the continuous flow NMR and EPR study of free radicals. Three fluorinated alkoxyamine initiators are synthesized and used to study the effect of adding carbon dioxide-philic fluorinated fragment in the nitroxide-mediated precipitation polymerizations of styrene in supercritical carbon dioxide. Two alkoxyamines have fluorinated functional handles built on the nitroxide part of the alkoxyamine whereas the third initiator has fluorinated functional handle on the benzyl-initiating fragment of the alkoxyamine. The partitioning of fluorinated nitroxide derivatives in supercritical carbon dioxide impacts on the controlled/living character and broadening of the molecular weight distributions but does not have any significant effect on the rate of precipitation polymerization in supercritical carbon dioxide

Synthesis and spin trapping properties of polystyrene supported trifluoromethylated cyclic nitrones.

Polystyrene supported fluorinated cyclic nitrone spin-traps: Resin-2-HFDMPO (2-hydroxymethyl-2-methyl-5-(trifluoromethyl)-3,4-dihydro-2H-pyrrole-1-oxide) and Resin-2-PFDMPO (2-(3-hydroxypropyl)-2-methyl-5-(trifluoromethyl)-3,4-dihydro-2H-pyrrole 1-oxide) containing a trifluoromethyl pyrroline-N-oxide core were developed to detect free radicals under flow conditions. A continuous flow EPR technique was used to evaluate the spin trapping properties of these tethered nitrones. While both resins trapped radicals, polymer supported nitrone Resin-2-PFDMPO with a longer and more flexible linker showed a more information rich spectrum than Resin-2-HFDMPO

Synthesis and spin trapping properties of polystyrene supported trifluoromethylated cyclic nitrones.

Polystyrene supported fluorinated cyclic nitrone spin-traps: Resin-2-HFDMPO (2-hydroxymethyl-2-methyl-5-(trifluoromethyl)-3,4-dihydro-2H-pyrrole-1-oxide) and Resin-2-PFDMPO (2-(3-hydroxypropyl)-2-methyl-5-(trifluoromethyl)-3,4-dihydro-2H-pyrrole 1-oxide) containing a trifluoromethyl pyrroline-N-oxide core were developed to detect free radicals under flow conditions. A continuous flow EPR technique was used to evaluate the spin trapping properties of these tethered nitrones. While both resins trapped radicals, polymer supported nitrone Resin-2-PFDMPO with a longer and more flexible linker showed a more information rich spectrum than Resin-2-HFDMPO

Synthesis and spin trapping properties of polystyrene supported trifluoromethylated cyclic nitrones.

Polystyrene supported fluorinated cyclic nitrone spin-traps: Resin-2-HFDMPO (2-hydroxymethyl-2-methyl-5-(trifluoromethyl)-3,4-dihydro-2H-pyrrole-1-oxide) and Resin-2-PFDMPO (2-(3-hydroxypropyl)-2-methyl-5-(trifluoromethyl)-3,4-dihydro-2H-pyrrole 1-oxide) containing a trifluoromethyl pyrroline-N-oxide core were developed to detect free radicals under flow conditions. A continuous flow EPR technique was used to evaluate the spin trapping properties of these tethered nitrones. While both resins trapped radicals, polymer supported nitrone Resin-2-PFDMPO with a longer and more flexible linker showed a more information rich spectrum than Resin-2-HFDMPO

Synthesis of fluorinated alkoxyamines and alkoxyamine-initiated nitroxide-mediated precipitation polymerizations of styrene in supercritical carbon dioxide

TIPNO (2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide)-alkoxyamine was found to give reasonably controlled/living nitroxide-mediated (NMP) precipitation polymerizations of styrene in supercritical carbon dioxide (scCO(2)). In contrast under the same conditions, the analogous SG1 (N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)nitroxide)-alkoxyamine gave higher rates of polymerization and inferior controlled/living character. The circumvention of the requirement for excess free (nitroxide](0) allowed the study of nitroxide partitioning effects in scCO(2) for three newly synthesized fluorinated alkoxyamines. Two alkoxyamines dissociated into scCO(2)-philic fluorinated TIPNO-nitroxide derivatives, while another contains a similar sized fluorinated "foot". Despite the increased steric bulk about the N-O bond for the novel fluorinated alkoxyamines, all polymerizations proceeded at a similar rate and level of control to the TIPNO system in solution (toluene). PREDICI simulations for the styrene/TIPNO system are used to support extensive partitioning effects observed in scCO(2) for the fluorinated alkoxyamines