Silsesquioxane-siloxane copolymers from polyhedral silsesquioxanes

Lichtenhan, Joseph D.; Vu, Ngo Q.; Carter, Jason A.; Gilman, Jeffrey W.; Feher, Frank J.

doi:10.1021/ma00060a053

Cited by 315 publications

(215 citation statements)

References 1 publication

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“…The POSS molecules have been successfully incorporated into many polymers, such as styryls, acrylics, liquid-crystalline polyesters, siloxanes, and polyamides. [22][23][24][25][26][27][28][29][30][31] Either by chemical or physical means, the POSS molecules can be dispersed in the polymer matrix by the adjustment of the chemical groups attached to the silicon atoms. The addition of POSS molecules can enhance many properties, such as heat resistance, oxygen permeation, and hardness.…”

Section: Introductionmentioning

confidence: 99%

Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions

Yang

Somani

et al. 2001

J Polym Sci B Polym Phys

145

105

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Crystallization studies at quiescent and shear states in isotactic polypropylene (iPP) containing nanostructured polyhedral oligomeric silsesquioxane (POSS) molecules were performed with in situ small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC). DSC was used to characterize the quiescent crystallization behavior. It was observed that the addition of POSS molecules increased the crystallization rate of iPP under both isothermal and nonisothermal conditions, which suggests that POSS crystals act as nucleating agents. Furthermore, the crystallization rate was significantly reduced at a POSS concentration of 30 wt %, which suggests a retarded growth mechanism due to the molecular dispersion of POSS in the matrix. In situ SAXS was used to study the behavior of shear-induced crystallization at temperatures of 140, 145, and 150°C in samples with POSS concentrations of 10, 20, and 30 wt %. The SAXS patterns showed scattering maxima along the shear direction, which corresponded to a lamellar structure developed perpendicularly to the flow direction. The crystallization half-time was calculated from the total scattered intensity of the SAXS image. The oriented fraction, defined as the fraction of scattered intensity from the oriented component to the total scattered intensity, was also calculated. The addition of POSS significantly increased the crystallization rate during shear compared with the rate for the neat polymer without POSS. We postulate that although POSS crystals have a limited role in shear-induced crystallization, molecularly dispersed POSS molecules behave as weak crosslinkers in polymer melts and increase the relaxation time of iPP chains after shear. Therefore, the overall orientation of the polymer chains is improved and a faster crystallization rate is obtained with the addition of POSS. Moreover, higher POSS concentrations resulted in faster crystallization rates during shear. The addition of POSS decreased the average long-period value of crystallized iPP after shear, which indicates that iPP nuclei are probably initiated in large numbers near molecularly dispersed POSS molecules.

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Section: Introductionmentioning

confidence: 99%

Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions

Yang

Somani

et al. 2001

J Polym Sci B Polym Phys

145

105

View full text Add to dashboard Cite

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“…There are few attempts to improve the physical properties by the introduction of polyhedral oligomeric silsesquioxane (POSS) unit in main chain of polysiloxane in place of the bulky and rigid organic moieties [12][13][14]. Moreover, incorporation of POSS unit in backbone of the linear step-condensed polymer in definite structure was quite difficult as the polycondensation of POSS having multiple reactive sites of equivalent reactivity with di-functional monomers typically generates insoluble cross-linked products [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Polysilsesquioxanes with Double-Decker Silsesquioxane Repeating Units

Hoque¹,

Kawakami²

2016

J. Sci. Res.

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Polysilsesquioxanes were synthesized with end functional double-decker silsesquioxanes (DDSQ) and the polymers were characterized with 1 H NMR, 29 Si NMR and size exclusion chromatography (SEC). Polysilsesquioxane containing iso-butyl end capped DDSQ showed better solubility compared to that of methyl end capped DDSQ. Thermal properties investigated with TGA showed that the polymers exhibited exceptionally high stabilities in the range of 470-530°C even in both nitrogen and air atmosphere. The average residual weights of the polymers at 760°C were around 80% in the nitrogen atmosphere.

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“…2 There are several approaches for chemical incorporation of POSS into polymers including monofunctional POSS cages grafted onto polymer chains as a pendant group. 9 Polymerisation techniques such as ring-opening 8,10,11 radical 12,13 or condensation polymerisation 14 may be used to incorporate monofunctional POSS into host polymers.…”

Section: Introductionmentioning

confidence: 99%

Impact of End-Tethered Polyhedral Nanoparticles on the Mobility of Poly(dimethylsiloxane)

et al. 2015

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A series of dumbbell-shaped nanocomposite materials of poly(dimethylsiloxanes) (PDMSs) and polyhedral oligomeric silsesquioxanes (POSSs) were synthesized through hydrosilylation reactions of allyl-and vinyl-POSS and hydrideterminated PDMS. The chemical structures of the dumbbellshaped materials, so-called POSS-PDMS-POSS triblocks, were characterized by 1 H NMR and FT-IR spectroscopy. The molecular weights of the triblock polymers were determined by gel permeation chromatography (GPC). Their size was analyzed by small-angle neutron scattering (SANS) and pulsed-field gradient stimulated echo (PFG STE) NMR experiments. The impact of POSS on the molecular mobility of the PDMS middle chain was observed by using 1 H spin−spin (T 2 ) relaxation NMR. In contrast to the PDMS melts, the triblocks showed an increase in mobility with increasing molecular weight over the range studied due to the reduced relative concentration of constraints imposed by the end-tethered nanoparticles. The triblock systems were used to compare the impact of tethered nanoparticles on the mobility of the linear component compared to the mobility of the polymer in conventional blended nanocomposites. The tethered nanoparticles were found to provide more reinforcement than physically dispersed particles especially at high molecular weights (low particle concentration). The physical blends showed an apparent percolation threshold behavior.

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Silsesquioxane-siloxane copolymers from polyhedral silsesquioxanes

Cited by 315 publications

References 1 publication

Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions

Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions

Synthesis of Polysilsesquioxanes with Double-Decker Silsesquioxane Repeating Units

Impact of End-Tethered Polyhedral Nanoparticles on the Mobility of Poly(dimethylsiloxane)

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