Melting points of symmetric oligomeric triblock copolymers (type pep) of ethylene and propylene oxides

Šimek, Lubomı́r; Petřík, Stanislav; Hadobaš, František; Bohdanecký, M.

doi:10.1016/0014-3057(90)90256-4

Cited by 7 publications

(9 citation statements)

References 8 publications

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“…We note here that the amount of crystallinity is low, which most likely depends on the low molecular weight of the PEO. The lower crystallinity and lower melting points for blocks compared to homopolymers of the same molecular weight are generally observed and are related to increased fluctuations in the vicinity of the amorphous block …”

Section: Discussionmentioning

confidence: 99%

“…Studies of semicrystalline PEO/PPO copolymers in the absence of solvent show that the polymeric system forms well-ordered lamellar domains. Experimental results show that the crystalline structure of the PEO in the semicrystalline aggregates depends on the length of the PEO chain, the length of the amorphous PPO block, and the copolymer architecture. ,,,,, Theoretical work by Whitmore et al . shows that chain folding leads to a less dense packing of the amorphous blocks.…”

Section: Introductionmentioning

confidence: 99%

“…The poly(ethylene oxide) homopolymer is crystalline at ambient temperatures if the molecular weight is larger than approximately 1000 . The melting procedure of the PEO homopolymer depends on the polymer molecular weight.…”

Section: Introductionmentioning

confidence: 99%

“…At low molecular weight (<4000), the polymer has an extended conformation, although several degrees of lamellar chain folding may exist at larger molecular weight during the melting procedure . The melting points of copolymers with PEO blocks are lower than these of PEO homopolymers having the same number of ethylene oxide units. ,, The degree of crystallinity is also significantly lower than that of the homologous homopolymer. , A lamellar structure is the most common mesostructure if one block is partly crystalline, but hexagonal structures have been reported for PDMS/PEO block copolymers …”

Section: Introductionmentioning

confidence: 99%

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Thermotropic and Lyotropic Behavior of a PEO−PPO−PEO Block Copolymer

Svensson

Olsson

2000

Macromolecules

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The phase behavior of the (EO)19(PO)43(EO)19/p-xylene system (where EO is ethylene oxide and PO is propylene oxide) with temperature is discussed. In this block copolymer the end blocks are crystallizable, and the middle block is noncrystallizable. Several techniques were used to delineate the phase boundaries (SAXS, WAXS, 1H NMR, 2H NMR, and DSC). An anisotropic region with a lamellar structure with semicrystalline PEO domains and amorphous PPO domains is formed at low temperatures and high copolymer concentrations. The lamellar structure has a one-dimensional swelling with increasing p-xylene concentration. The driving force for forming the anisotropic region is that the PEO crystallize at low temperatures. The amount of crystallinity in the system and the interfacial area per PEO block in the ordered region depend on the temperature and the sample composition. At high temperatures and low copolymer concentrations the system contains an isotopic solution phase.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermotropic and Lyotropic Behavior of a PEO−PPO−PEO Block Copolymer

Svensson

Olsson

2000

Macromolecules

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“…In the context of a “simple” diblock copolymer design, understanding and exploiting the optimal blend of (directional) molecular interactions and full synthetic control is still in its infancy. Even though the development of “high χ–low N ” BCPs has led to ever smaller domain spacings, the general trend is to avoid the use of crystalline blocks, and the extent of long-range order in the resulting systems is often limited. ,,− A notable exception here is the work of Booth and co-workers on poly(ethylene oxide- block -propylene oxide), − poly(ethylene oxide- block -butylene oxide), − and poly(ethylene oxide- block -methylene) − in di- and triblock configurations.…”

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confidence: 99%

Amplifying (Im)perfection: The Impact of Crystallinity in Discrete and Disperse Block Co-oligomers

et al. 2017

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Crystallinity is seldomly utilized as part of the microphase segregation process in ultralow-molecular-weight block copolymers. Here, we show the preparation of two types of discrete, semicrystalline block co-oligomers, comprising an amorphous oligodimethylsiloxane block and a crystalline oligo-l-lactic acid or oligomethylene block. The self-assembly of these discrete materials results in lamellar structures with unforeseen uniformity in the domain spacing. A systematic introduction of dispersity reveals the extreme sensitivity of the microphase segregation process toward chain length dispersity in the crystalline block.

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Melt viscosity of oligomeric triblock copolymers (type PEP) of ethylene and propylene oxides

Šimek

Petřík²,

Bohdanecký

1994

J of Applied Polymer Sci

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SYNOPSISMelt viscosity I) a t 25°C of four oligomeric triblock copolymers consisting of a central block of ethoxamer units and two end blocks of propoxamer units (PEP) ( M , X = 1 and 2; mole fraction of ethoxamer units xE = 0.41,0.57, and 0.74) was analyzed in terms of the theory advanced by Berry and Fox. The structure-dependent factor F ( X ) was deduced from the intrinsic viscosity data, and the mean friction factor per friction center < was computed from I) and F ( X ) . At a fixed molecular weight, it increases with increasing x E .The dependence of < versus X E was compared with curves computed from the data for INTRODUCTIONThe Newtonian viscosity of liquid linear polymers can be expressed by the equation (cf. Ref. 1 ) where F ( X ) is the structure-dependent factor and {is the friction factor per main chain atom or atomic group. The former is controlled by the large-scale structure and configuration of the chain whereas the latter is controlled by local intra-and intermolecular forces between the segments of the chain. Below the critical entanglement molecular weight, M,, the structure factor is written as where NA is the Avogadro constant, Z is the number of main chain atoms or atomic groups considered as friction centers, M is the polymer molecular weight, With copolymers, both the structure and friction factors depend on the composition. The effect of composition on the former can easily be predicted. The m, values are obtained by simple interpolation between those for homopolymers, and the specific volume can be measured. The values of ( s~)~/ M are deduced from dilute solution properties, e-g., intrinsic viscosity, by standard procedures (cf. Ref. 6 ) . On the contrary, the effect of composition on the friction factor is an open problem that has so far been examined with two or three copolymersIn this work we discuss the dependence on copolymer composition of the melt viscosity of triblock copolymers (type PEP) consisting of a central block of ethylene oxide units and two end blocks of propylene oxide units. From the intrinsic viscosity data we evaluate the structure-dependent factor F ( X ) .By combining it with the melt viscosity, we calculate the friction factor and compare it with the values computed from parameters B, T o , and r0 for homopolymers (PEO, PPO ) . To have a firm basis for this work we first review and analyze the data on these parameters, which are available in literature. EXPERIMENTAL PolymersHydroxy-terminated triblock copolymers PEP ( Table I) were provided by the Petrochemical Research Institute, Prievidza (Slovak Republic) and were identical with those used Acetyl-terminated samples were provided by Dr. F. HadobaFj (Research Institute for Plastics and Rubber Technology, Zlin, Czech Republic). They were prepared by heating dry samples of PEP with acetanhydride and pyridine (weight ratio 3 : 1 : 6 ) for 4 h to 80°C. The conversion was almost complete, the hydroxyl content being decreased from 3.2-3.9 wt % to 0.1-0.4 wt %.

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Melting points of symmetric oligomeric triblock copolymers (type pep) of ethylene and propylene oxides

Cited by 7 publications

References 8 publications

Thermotropic and Lyotropic Behavior of a PEO−PPO−PEO Block Copolymer

Thermotropic and Lyotropic Behavior of a PEO−PPO−PEO Block Copolymer

Amplifying (Im)perfection: The Impact of Crystallinity in Discrete and Disperse Block Co-oligomers

Melt viscosity of oligomeric triblock copolymers (type PEP) of ethylene and propylene oxides

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