A semiempirical quantum mechanical study of the cationic homopolymerization of expanding and potentially expanding monomer systems

et al. 2004

ABSTRACT:The objective was to study the photocationic polymerization of an expanding monomer, 1,5,7,11-tetraoxaspiro[5.5]undecane (TOSU), and an aromatic dioxirane, bisphenol A diglycidyl ether (BADGE). Both homopolymerizations and binary polymerizations were conducted. The homopolymer, poly(TOSU), was found to be a linear poly(carbonate), which was soluble in acetone. Poly-(BADGE) products contained ether linkages in addition to primary and secondary alcohol functionalities. Binary polymerization products varied depending on the irradiation time and length of dark cure.13 C-NMR analysis of binary polymerizate products revealed peaks not seen in homopolymer spectra consistent with the formation of copolymer linkages. Mass spectrometry data revealed peaks consistent with oligomers that contained both TOSU and BADGE mer units. The structures of key reaction products were proposed.

Section: Methodsmentioning

confidence: 99%

“…Computational methods based on quantum mechanics have recently been applied to determine activation energies and enthalpies of polymerization for a variety of monomers 25–27. These calculations can help predict which reactions are most favored energetically.…”

Section: Introductionmentioning

confidence: 99%

Photopolymerization of an expanding monomer with an aromatic dioxirane

Smith

et al. 2004

“…Theoretical calculations (enthalpy, activation energy) and modeling of transition states and reaction pathways for both homopolymerization and copolymerization of 1,5,7,11-tetraoxaspiroalkanes have been conducted. [27][28][29] …”

Section: Introductionmentioning

confidence: 99%

Tetraoxaspiroalkanes for polymerization stress reduction of Silorane resins

Chen

et al. 2008

This study involved the synthesis and characterization of tetraoxaspiroalkane monomers and evaluated their potential to reduce polymerization stress when formulated in a Silorane resin system. The tetraoxaspiroalkane monomers had two main structural features (a) two different types of core ring structures (a 1,5,7,11-tetraoxaspirocyclic ring or a 2,4,8,10-tetraoxaspirocyclic ring) and (b) four different types of ring substituents (normal alkyl, allyloxyalkyl, trimethylsilylalkyl, or oxabicycloalkyl). The resin formulations contained (a) 20 mol % of a 1,5,7,11-or 2,4,8,10-tetraoxaspiroalkyl monomer; (b) a phenylmethylsilane containing two oxabicycloheptyl groups; (c) a cyclotetrasiloxane containing four oxabicycloheptyl groups; and (d) a photocationic initiator system. Three main aspects were studied (a) the photoreactivity of the formulations using PDSC, (b) photopolymerization stress, and (c) mechanical properties (flexural elastic modulus, ultimate strength, and work of fracture) which were measured using an electromagnetic mechanical testing machine. The main findings were (a) formulations containing 2,4,8,10-tetraoxaspiroalkane monomers had measured net enthalpies greater than those containing 1,5,7,11-tetraoxaspiroalkane monomers, and above those calculated for addition of an inert diluent; (b) all formulations containing tetraoxaspiroalkane monomers exhibited photopolymerization stress values that were 40-99% less than the nonaddition control; (c) the formulation containing a 1,5,7,11-tetraoxaspiroalkane monomer with an oxirane functionality had mechanical properties that were not significantly different from the nonaddition control.

“…Cationically initiated reactions at the TOSU center commence with an essentially irreversible protonation of one of the spiro oxygens to form a carbocation that becomes the polymerizing species. We have carried out extensive theoretical calculations on both the homopolymerization and copolymerization of spiroorthocarbonates 19–21…”

Section: Introductionmentioning

confidence: 99%

Photopolymerization of a novel tetraoxaspiroundecane and silicon‐containing oxiranes

Chen

et al. 2006

New multifunctional silorane-based systems were investigated, with respect to their photoreactivity, as potential matrix resins for low-shrinkage/stress dental composites. The objective of this investigation was to synthesize and evaluate the reactivity of a silicon-analogue oxaspirocyclic monomer with silorane-based matrix resin systems during visible-light polymerization. The experimental formulations contained (1) a silicon-containing 1,5,7,11-tetraoxaspiro[5.5]undecane (TOSU-IV), (2) a phenylmethylsilane containing two cyclohexyloxiranyl groups, (3) a cyclotetrasiloxane containing four cyclohexyloxiranyl groups, and (4) a photocationic initiator system. Three main aspects were studied: (1) the photoreactivity of the tetraoxaspiroundecane (TOSU)/silorane reactant mixtures with differential scanning photocalorimetry, (2) oxirane ring-opening reactions of siloranes during binary photopolymerization with Fourier transform infrared (FTIR), and (3) oxaspirocyclic ring-opening reactions of the TOSU reactant during homophotopolymerization and binary photopolymerization with FTIR and NMR. A diallyl ether precursor of TOSU-IV was also included in selected studies. The main findings were as follows: (1) a feasible route for the successful synthesis of a silicon analogue (TOSU-IV) was developed; (2) TOSU-IV was compatible and photoreactive, making possible the reduction of polymerization stress in silorane-based matrix resins; and (3) spectroscopic evidence for both oxirane and oxaspirocyclic ring opening during the visible-light photopolymerization of the test formulations was found.