Electro-optic properties of thiol-ene polymer stabilized ferroelectric liquid crystals

Beckel, Eric R.; Cramer, Neil B.; Harant, Adam W.; Bowman, Christopher N.

doi:10.1080/02678290310001605910

Cited by 18 publications

(10 citation statements)

References 33 publications

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“…Since the response time τ is directly proportional to the effective viscosity η via τ = η/P S E, the equivalent trend is also observed for the viscosity as a function of polymer network content ( Figure 9b ). Such behaviour has been reported by several authors [ 52 – 55 ], but it should be pointed out, that results of the opposite behaviour have also been published, i.e. , an increase in viscosity with increasing polymer concentration [ 56 ].…”

Section: Effects On Smc* Materials Parameterssupporting

confidence: 65%

A Review of Polymer-Stabilized Ferroelectric Liquid Crystals

Dierking

2014

Materials

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The polymer stabilized state of ferroelectric liquid crystals (FLC) is reviewed; and the effect of a dispersed polymer network in an FLC outlined and discussed. All fundamental material aspects are demonstrated; such as director tilt angle; spontaneous polarization; response time and viscosity; as well as the dielectric modes. It was found that the data can largely be explained by assuming an elastic interaction between the polymer network strands and the liquid crystal molecules. The elastic interaction parameter was determined; and increases linearly with increasing polymer concentration.

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Section: Effects On Smc* Materials Parameterssupporting

confidence: 65%

A Review of Polymer-Stabilized Ferroelectric Liquid Crystals

Dierking

2014

Materials

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“…9 Since then, thiol-ene reactions have undergone considerable investigation to determine monomer effects on polymerization rates, 1,[10][11][12][13][14][15][16] effects of oxygen, 7,8,17 effects of a thiol-olefin charge-transfer complex and the co-oxidation reaction, [18][19][20][21] thiol-(meth)acrylate copolymerizations, 6,22,23 initiatorless polymerizations, 8,22,24 and applications to polymer stabilized liquid crystals. [25][26][27][28] However, several aspects of thiol-ene polymerizations, including reaction order and kinetics, 2,3 initiation without photoinitiators, 8,22,24 and the dark reaction 19,20,29,30 are still not well understood.…”

Section: Introductionmentioning

confidence: 99%

Thiol−Ene Photopolymerization Mechanism and Rate Limiting Step Changes for Various Vinyl Functional Group Chemistries

et al. 2003

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The mechanism and kinetics of thiol-ene photopolymerizations utilizing a tetrafunctional thiol monomer copolymerized with acrylate, norbornene, vinyl ether, and vinyl silazane functionalized ene monomers are successfully modeled and experimentally characterized. Modeling predictions demonstrate that the reaction orders in thiol-ene systems are controlled by the ratio of thiyl radical propagation to chain transfer kinetic parameters (k p/kCT). Ratios of kinetic parameters (kp/kCT) were found to vary significantly with the ene functional group chemistry and to have a dramatic impact on polymerization kinetics. For high ratios of kp/kCT, polymerization rates are first order in thiol functional group concentration and nearly independent of ene functional group concentration. For kp/kCT values near unity, polymerization rates are approximately 1 /2 order in both thiol and ene functional group concentrations. When kCT is much greater than kp, polymerization rates are first order in ene functional group concentration and nearly independent of the thiol functional group concentration. In thiol-allyl ether and thiol-acrylate systems, the step growth polymerization rates are first order in thiol functional group concentration (Rp ∝ [SH]). For thiol-norbornene and thiol-vinyl ether systems, polymerizations are nearly 1 /2 order in both thiol and ene functional group concentrations (Rp ∝ [SH] 1/2 [CdC] 1/2 ). In thiolvinyl silazane systems, polymerization rates are approximately first order in ene functional group concentration (Rp ∝ [CdC]) and independent of thiol functional group concentration. A theory is proposed which states that the effect of functional group chemistry on kp/kCT is controlled primarily by ene functional group electron density (kp) and carbon radical stability (kCT).

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“…44,45 As a result, several novel applications of thiol-ene polymers have been investigated including dental composites, 46,47 holographic gratings, [48][49][50] biodegradable materials for tissue engineering, [51][52][53] formation of nanoimprinted polymers [54][55][56] and stabilizing and aligning liquid crystals in polymer matrices. 50,57,58 Recently, Lee and Bowman used thiol-ene photopolymerizations for modifying silica nanoparticles using a variety of thiol-ene monomers and reaction conditions. 59 Using real-time infrared spectroscopy, it was shown that, even in the presence of a significant amount of nanoparticles, near-complete conversion of the monomers was achieved in most cases including the cases where multifunctional monomers forming cross-linked polymer structures were used.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization and Cleavage of Surface-Bound Linear Polymers Formed Using Thiol−Ene Photopolymerizations

2008

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The formation of linear polymer films using thiol-ene photopolymerizations was investigated by grafting thiol-ene films on the surface with subsequent cleavage and polymer analysis. Silica nanoparticles were first modified with an acrylated silane molecule, and then a dithiol was reacted to this surface using a base catalyzed thiol-acrylate conjugate addition reaction to prepare a uniform surface presenting thiol groups attached to the surface with a cleavable ester linkage. Photopolymerization of difunctional thiol and ene monomers present in various stoichiometric ratios was carried out in the presence of the nanoparticles, and a thiol-ene film was attached to the surface. The polymer film was cleaved from the surface using acid-catalyzed hydrolysis and separated from the particles. It was found that the particle presence does not affect the polymerization of thiol-ene polymers in bulk; however, the presence of surface thiols changes the relative stoichiometry of the thiol and ene monomers at the surface and hence strongly affects the molecular weight of the attached polymer. The number average and the weight average molecular weight of the unattached polymers ranged from 900 to 12,600 g/mol and 1500 to 25,700 g/mol, respectively, as the thiol:ene ratio in the bulk increased from 0.6 to 1. The highest molecular weight of the grafted polymers (M n ) 1600 g/mol, M w ) 2700 g/mol) was achieved when the thiol:ene ratio was close to 0.77:1 in the bulk and decreased monotonically for both higher and lower stoichiometric ratios. When the polymerization rate was decreased and the time scales for reaction increased, the grafted polymer molecular weight increased for stoichiometric thiol-ene monomer mixtures, because the relative effect of surface thiols was decreased.

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Electro-optic properties of thiol-ene polymer stabilized ferroelectric liquid crystals

Cited by 18 publications

References 33 publications

A Review of Polymer-Stabilized Ferroelectric Liquid Crystals

A Review of Polymer-Stabilized Ferroelectric Liquid Crystals

Thiol−Ene Photopolymerization Mechanism and Rate Limiting Step Changes for Various Vinyl Functional Group Chemistries

Synthesis, Characterization and Cleavage of Surface-Bound Linear Polymers Formed Using Thiol−Ene Photopolymerizations

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