Synthesis of Linear Polysiloxanes

Chojnowski, Julian; Cypryk, Marek

doi:10.1007/978-94-011-3939-7_1

Cited by 56 publications

(34 citation statements)

References 123 publications

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“…Silicone materials are well‐known for their chemical and mechanical stability. These unique properties are attributed to the

Si ‐ O

linkage, exhibiting a higher bond strength (

444 kJ / mol

) and longer bonding distance (

\sim 1.64

Å) compared with

C ‐ C

linkages (

348 kJ / mol

and

\sim 1.54

Å) . The siloxane bond has a partial ionic character, resulting from the electronegativity difference between

Si

and

normalO

(1.8 and 3.5 on the Pauling scale) and a partial double bond formed by the vacant silicone 3 d and oxygen 2 p orbitals .…”

Section: Introductionmentioning

confidence: 99%

Fracture and thermal aging of resin‐filled silicone elastomers

Yeh

Dowland

Schmidt

et al. 2015

J Polym Sci B Polym Phys

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The role of nano-sized resin fillers on the fracture and viscoelastic behavior of silicones was examined in the context of thermal aging. Systems with different resin volume fractions and resin glass transition temperatures were compared. X-ray scattering patterns were collected over a wide range of q-values in order to provide insight into the physical structure of the silicone elastomers. Additionally, tensile, dynamic mechanical, and fracture tests were performed. Temperature shift factors obtained from the dynamic mechanical data were used to obtain master plots of the fracture toughness as a function of reduced crack velocity. The elastic modulus for each of the materials increased as a function of thermal aging time, and the high-temperature fracture behavior for each of the systems was reduced to values characteristic of unfilled systems after 14 days of aging at 200 8C. In order to obtain an accurate representation of the viscoelastic response of the materials in the megahertz frequency regime, quartz crystal resonators were used to measure mass changes and rheological properties after thermal aging. The results are consistent with a simple picture of dynamic heterogeneity, where high toughness requires that regions with different dynamic properties exist within the sample.

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“…Silicone materials are well‐known for their chemical and mechanical stability. These unique properties are attributed to the

Si ‐ O

linkage, exhibiting a higher bond strength (

444 kJ / mol

) and longer bonding distance (

\sim 1.64

Å) compared with

C ‐ C

linkages (

348 kJ / mol

and

\sim 1.54

Å) . The siloxane bond has a partial ionic character, resulting from the electronegativity difference between

Si

and

normalO

(1.8 and 3.5 on the Pauling scale) and a partial double bond formed by the vacant silicone 3 d and oxygen 2 p orbitals .…”

Section: Introductionmentioning

confidence: 99%

Fracture and thermal aging of resin‐filled silicone elastomers

Yeh

Dowland

Schmidt

et al. 2015

J Polym Sci B Polym Phys

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“…This eight-membered ring, which certainly also exists in the polymerizations carried out at 30°C over a short period of time but in negligible amount (Figure 4), might result from a backbiting side reaction (intramolecular reaction) very usual with cyclic siloxane and siloxazane compounds. 14,22 It is also noteworthy that, in such conditions, the 29 Si NMR spectra of the polymers exhibit the signals of various silicon environments certainly resulting from simultaneous intermolecular redistributions of siloxazane units (randomization by chain transfer) (Figure 3b). Nevertheless, in the specific conditions used, as initiation step, the side-reaction Table 1).…”

Section: Resultsmentioning

confidence: 96%

“…This situation is different from that reported for anionic ring-opening polymerization of hexamethylcyclotrisiloxane D 3 which gives, at equilibrium, except at very high temperature, a very low amount of initial monomer. 22 This might be related to the low polymerization enthalpy of monomer 1 compared to that of D 3 .…”

Section: Assuming That For Polymers [Mmentioning

confidence: 98%

“…Taking into account the kinetic order relative to DMF (close to 1), the high effectivity of the ion-ion interactions of silanolate anions, 22 and the facility of the Li + ion to be complexed by DMF, the most probable structure of these active species is that of ion pairs externally solvated by DMF, in equilibrium with inactive aggregated ion pairs, presumably dimers since the kinetic order value is around 1/2 (eq 5). Nevertheless, the treatment of kinetic data according to the method proposed by Penczeck and colleagues 25 does not agree with an aggregation number m of 2.…”

Section: Assuming That For Polymers [Mmentioning

confidence: 99%

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Equilibrium Anionic Ring-Opening Polymerization of a Six-Membered Cyclosiloxazane

et al. 2007

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The anionic ring-opening polymerization of heptamethyl-1,3-dioxa-5-aza-2,4,6-trisilacyclohexane, initiated with organolithium compounds, has been investigated. With the addition of dimethylformamide (DMF), the polymerization is controlled. Backbiting reactions are limited and give a unique specific cyclic compound in low proportion. Thermodynamic and kinetic studies indicate that such polymerization is equilibrated. The apparent rate constants of propagation and depolymerization along with the thermodynamic parameters (enthalpy and entropy) of the polymerization have been calculated. The active species are ion pairs externally solvated by DMF in equilibrium with unreactive aggregated ion pairs.

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“…Consequently, siloxanes are a fitting material selection for implementation with a thiol-ene-based setting/polymerization reaction given their noted flexibility, mechanical integrity, and biocompatibility [16]. Siloxanes are also highly amenable to functionalization, and multifunctional polymers can be readily synthesized through the condensation of pendant –Cl, -OH, or –OR groups by a variety of catalytic species [17]. Hence, the primary objective of this study is to evaluate the use of thiol- and ene-functionalized siloxanes as a viable alternative to current impression materials.…”

Section: Introductionmentioning

confidence: 99%

Thiol-ene functionalized siloxanes for use as elastomeric dental impression materials

2014

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Objectives-Thiol-and allyl-functionalized siloxane oligomers are synthesized and evaluated for use as a radical-mediated, rapid set elastomeric dental impression material. Thiol-ene siloxane formulations are crosslinked using a redox-initiated polymerization scheme, and the mechanical properties of the thiol-ene network are manipulated through the incorporation of varying degrees of plasticizer and kaolin filler. Formulations with medium and light body consistencies are further evaluated for their ability to accurately replicate features on both the gross and microscopic levels. We hypothesize that thiol-ene functionalized siloxane systems will exhibit faster setting times and greater detail reproduction than commercially available polyvinylsiloxane (PVS) materials of comparable consistencies.Methods-Thiol-ene functionalized siloxane mixtures formulated with varying levels of redox initiators, plasticizer, and kaolin filler are made and evaluated for their polymerization speed (FTIR), consistency (ISO4823.9.2), and surface energy (goniometer). Feature replication is evaluated quantitatively by SEM. The T g , storage modulus, and creep behavior are determined by DMA.Results-Increasing redox initiation rate increases the polymerization rate but at high levels also limits working time. Combining 0.86 wt% oxidizing agent with up to 5 wt% plasticizer gave a working time of 3 min and a setting time of 2 min. The selected medium and light body thiol-ene formulations also achieved greater qualitative detail reproduction than the commercial material and reproduced micrometer patterns with 98% accuracy.Significance-Improving detail reproduction and setting speed is a primary focus of dental impression material design and synthesis. Radical-mediated polymerizations, particularly thiol-ene reactions, are recognized for their speed, reduced shrinkage, and 'click' nature.

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Synthesis of Linear Polysiloxanes

Cited by 56 publications

References 123 publications

Fracture and thermal aging of resin‐filled silicone elastomers

Fracture and thermal aging of resin‐filled silicone elastomers

Equilibrium Anionic Ring-Opening Polymerization of a Six-Membered Cyclosiloxazane

Thiol-ene functionalized siloxanes for use as elastomeric dental impression materials

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