Selective determination of glass transition temperature and vibrational properties at the chain end of polystyrene by Fourier transform infrared measurement in combination with deuterium-labeling

Miwa, Yohei; Urakawa, Osamu; Nobukawa, Shogo; Kutsumizu, Shoichi

doi:10.1016/j.polymer.2015.01.021

Cited by 11 publications

(7 citation statements)

References 62 publications

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“…The end groups possess excess free volume and configurational entropy and deficient intermolecular constraints, leading to higher mobility. [27][28][29][30]36 Using anionically polymerized PS standards with MWs ranging from ∼2 to ∼100 kg/mol, Hintermeyer et al 4 obtained the same T g −MW relationship by differential scanning calorimetry (DSC) as that reported by Fox and Flory from a combined dilatometry (for T g )/viscosity (for M n ) study. 2 Similar results were obtained by Rudin et al, who compared anionically and thermally polymerized PS down to MWs of ∼2 kg/mol.…”

Section: Introductionmentioning

confidence: 66%

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

et al. 2016

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Important, yet unexplored effects of chemically distinct initiator fragments incorporated at chain ends in linear polymer are investigated in depth. Polystyrene (PS) samples of a wide range of molecular weight (MW) were synthesized by conventional free radical polymerization and controlled radical polymerization using seven different initiators and compared with anionically polymerized PS. The initiator fragments incorporated during polymerization have major consequences on the glass transition temperature (T g) and dynamic fragility of low MW PS. For example, with ∼4 kg/mol PS, the T g onset value and fragility can be tuned from ∼334 K and ∼65, respectively, with dodecanethiol and hydrogen atom chain ends to ∼367 K and ∼130, respectively, with cyanopentanoic acid chain ends. A similar high T g and high fragility were measured with isobutyric acid/SG1 nitroxide chain ends. These remarkable effects, with a greater than 30 K difference in T g and a factor of 2 difference in fragility, indicate that chain ends in low MW PS homopolymer play an “outsize” role in comparison to comonomer units in perturbing properties that are sensitive to the density of chain ends. The T g results also provide further direct evidence against any correlation between the MW at which the T g–MW dependence saturates and entanglement MW. Instead, the perturbation of T g by the combined effects of a reduction in MW (increase in chain-end density) and chain-end structure correlates one-to-one within error with the perturbation of fragility. These results suggest that the susceptibility of fragility to be perturbed is key to the susceptibility of T g to be perturbed.

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Section: Introductionmentioning

confidence: 66%

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

et al. 2016

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“…The MW dependence observed in our study is in major agreement with both Savin et al and Dang et al Reductions in T g can be attributed to enhanced influence from free chain ends at low MW. Zhang and Torkelson recently stated that “the role of chain ends in providing a greater degree of conformational freedom is central to the MW dependence of T g .” This is because free chain ends enhance free volume and configurational entropy of the polymer chains. − As MW decreases, enhanced configurational freedom provided by free chain ends reduces requirements for cooperative mobility and hence T g decreases. In the case of Si-PS, one end of the chains is immobilized.…”

Section: Resultsmentioning

confidence: 99%

Polystyrene-Grafted Silica Nanoparticles: Investigating the Molecular Weight Dependence of Glass Transition and Fragility Behavior

Askar

Torkelson

2017

Macromolecules

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Polymer-tethered nanoparticles provide a strategy to improve particle dispersion in polymer nanocomposites and as materials themselves can exhibit self-healing behavior and enhanced mechanical properties. The few studies that previously characterized the glass transition temperature (T g) behavior of neat polymer-grafted nanoparticles in the absence of a polymer matrix largely focused on average T g response. We synthesized polystyrene-grafted silica nanoparticles (Si-PS) via ARGET ATRP, achieving the densely grafted state. Using differential scanning calorimetry, we investigated the brush molecular weight (MW) dependence of T g, T g breadth, heat capacity jump (ΔC p ), and fragility from 12 to 98 kg/mol. Compared with free PS chains of the same MW, brush T g increases by 1–2 °C, brush T g breadth remains unchanged within error down to 36 kg/mol and increases by 3–4 °C at brush MWs of 12 and 13 kg/mol, and brush ΔC p and fragility remain unchanged within error down to 52 kg/mol and then decrease with decreasing MW. Evidence of a significant T g gradient from near the nanoparticle graft interface to near the free chain end was obtained for the first time via fluorescence of a pyrenyl dye labeled at specific regions along the brush chain length. In relatively high MW brushes, T g = ∼116 °C near the graft interface and T g = ∼102 °C near the chain end. Comparisons are made to results recently reported for similar PS brushes densely grafted to a flat substrate, which indicate that a larger T g gradient is evident in a grafting geometry involving a flat interface as compared with a spherical nanoparticle interface. Other comparisons are also made with glass transition and fragility behaviors reported in the flat substrate geometry. Results of this study and others will help to better understand nanocomposites and tailor them for optimal properties.

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“…Some studies suggest that lower entanglement means a higher concentration of chain ends, which lead to lower T g . [ 107–109 ] Others indicate that entanglements influence the remaining shift and physical properties near T g . [ 110 ] Bernazzani et al.…”

Section: Effect Of Entanglement On the Polymer Propertiesmentioning

confidence: 99%

Control of Polymer Properties by Entanglement: A Review

Kong

Yang

Zhang

et al. 2021

Macro Materials & Eng

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Chain entanglement, either cohesional or topological, distinguishes polymers from other engineering materials. It impedes the movement of molecular segments and influences the polymer rheology, morphology, and mechanical properties. Although a high level of entanglement can increase the polymer toughness, excessive entanglement should be avoided because it causes a high melt viscosity making the processing difficult. This review tended to elucidate the influence of entanglement on the polymer structure, determining the material properties and processability. A wide range of methods used to fine control the degrees of chain entanglement are summarized. The methods are applicable to polymers in solutions, melts, and condensed states with advantages and limitations discussed in detail. The authors also examined the effect of the entanglement on polymer crystallization—the mechanism remains a controversial issue. This review will provide general guidance to designing and processing polymer materials with desired properties via a rational route of controlling the chain entanglement.

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Selective determination of glass transition temperature and vibrational properties at the chain end of polystyrene by Fourier transform infrared measurement in combination with deuterium-labeling

Cited by 11 publications

References 62 publications

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

Dramatic Tunability of the Glass Transition Temperature and Fragility of Low Molecular Weight Polystyrene by Initiator Fragments Located at Chain Ends

Polystyrene-Grafted Silica Nanoparticles: Investigating the Molecular Weight Dependence of Glass Transition and Fragility Behavior

Control of Polymer Properties by Entanglement: A Review

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