The relationship between the equilibrium melting temperature and the supermolecular structure of several polyoxetanes and polyethylene oxide

Murphy, Charles J.; Henderson, G. V. S.; Murphy, Elizabeth A.; Sperling, L. H.

doi:10.1002/pen.760271103

Cited by 7 publications

(1 citation statement)

References 30 publications

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“…1 µm) films of polyethylene oxide (PEO) [ 21 ]. There, the polymer film was first completely melted at 80 °C, i.e., well above the equilibrium melting temperature (

) and then quenched to a low crystallization temperature to ensure fast growth and a high nucleation density [ 21 , 22 ]. These crystalline PEO films were heated to

, slightly lower than

, yielding a controlled number of remaining crystalline seeds.…”

Section: Introductionmentioning

confidence: 99%

Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

2021

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We examined the formation of self-seeded platelet-like crystals from polystyrene-block-polyethylene oxide (PS-b-PEO) diblock copolymers in toluene as a function of polymer concentration (c), crystallization temperature (TC), and self-seeding temperature (TSS). We showed that the number (N) of platelet-like crystals and their mean lateral size (L) can be controlled through a self-seeding procedure. As (homogeneous) nucleation was circumvented by the self-seeding procedure, N did not depend on TC. N increased linearly with c and decayed exponentially with TSS but was not affected significantly by the time the sample was kept at TSS. The solubility limit of PS-b-PEO in toluene (c*), which was derived from the linear extrapolation of Nc→ 0 and from the total deposited mass of the platelets per area (MCc→0), depended on TC. We have also demonstrated that at low N, stacks consisting of a (large) number (η) of uniquely oriented lamellae can be achieved. At a given TC, L was controlled by N and η as well as by ∆c=c−c∗. Thus, besides being able to predict size and number of platelet-like crystals, the self-seeding procedure also allowed control of the number of stacked lamellae in these crystals.

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“…1 µm) films of polyethylene oxide (PEO) [ 21 ]. There, the polymer film was first completely melted at 80 °C, i.e., well above the equilibrium melting temperature (

) and then quenched to a low crystallization temperature to ensure fast growth and a high nucleation density [ 21 , 22 ]. These crystalline PEO films were heated to

, slightly lower than

, yielding a controlled number of remaining crystalline seeds.…”

Section: Introductionmentioning

confidence: 99%

Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

2021

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Characterization of poly(3,3‐bisethoxymethyl oxetane) and poly(3,3‐bisazidomethyl oxetane) and their block copolymers

Murphy

Ntozakhe

Murphy

et al. 1989

J of Applied Polymer Sci

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SynopsisThe homopolymers, poly(3,3-bisethoxymethyl oxetane) (polyBEMO), poly(3,3-bisazidomethyl oxetane) (polyBAMO), and triblock copolymers based on these homopolymers and a statistical copolymer center block composed of BAMO and 3-azidomethyl-3-methyl oxetane AMMO were synthesized and characterized by differential scanning calorimetry, modulus-temperature, optical microscopy, membrane osmometry, and solution and melt viscosity. The values of K and a for the Mark-Houwink equation were found to be 7.29 x mL/g and 0.80, respectively, for polyBEMO at 25°C Using number-average molecular weights. Glass transition temperatures were in the range -25 to -40°C and melting temperatures were between 65 and 90°C for all polymers. The melting temperature was found to increase as expected with molecular weight. Melt viscosities of triblock copolymers with polyBAMO end blocks were at least an order of magnitude lower than those with polyBEM0 end blocks and clear optically, suggesting that the polyBAM0-based triblock copolymers formed one phase in the melt, while the polyBEMO-based triblock materials (milk white) phase separated. The addition of filler raised the melt viscosity to a level between that predicted by the Guth-Smallwood and the Mooney equations.

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Multiple endotherm melting behavior in relation to the morphology of poly[3,3‐ bis(ethoxymethyl) oxetane]

Fay

Murphy

Sperling

1990

J of Applied Polymer Sci

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SynopsisTwo crystalline melting peaks have been observed by differential scanning calorimetry for low molecular weight poly [3,3-bis(ethoxymethyl) oxetane] (polyBEM0) samples, M , < 1 X lo4 g/ mol, whereas only one melting peak has been observed for samples of higher molecular weight, M , 1 X 10' g/mol. Crystallization of low molecular weight samples at large supercoolings produces the lower melting form while low supercooling or annealing favors the higher melting species. Enthalpy of fusion values obtained by DSC for a multiple melting endotherm sample range from 28 to 39 J / g for crystallization temperatures from 58 to 35"C, respectively. Optical microscopy studies indicate that the lower melting peak corresponds to a spherulitic type morphology and the higher melting peak correlates to a fine grained crystal structure. Wide angle X-ray powder diffraction studies do not detect differences in the crystal structures of samples exhibiting either one or two melting peaks, which suggests that the multiple melting phenomenon is due to differences in morphology rather than the presence of different crystal forms.

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The relationship between the equilibrium melting temperature and the supermolecular structure of several polyoxetanes and polyethylene oxide

Cited by 7 publications

References 30 publications

Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

Self-Seeding Procedure for Obtaining Stacked Block Copolymer Lamellar Crystals in Solution

Characterization of poly(3,3‐bisethoxymethyl oxetane) and poly(3,3‐bisazidomethyl oxetane) and their block copolymers

Multiple endotherm melting behavior in relation to the morphology of poly[3,3‐ bis(ethoxymethyl) oxetane]

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