Rheooptical investigation of the transition behavior of polyphosphazenes

Russell, T. P.; Anderson, D. P.; Stein, R. S.; Desper, C. R.; Beres, J. J.; Schneider, N. S.

doi:10.1021/ma00139a029

Cited by 18 publications

(7 citation statements)

References 2 publications

(3 reference statements)

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“…30 demonstrates it quite obviously for PBFP 106). In X-ray fiber patterns of a mesomorphic sampie of PBFP, the first sharp reflection (11 A) is concentrated at the equator indicating the existence of the lateral order in the packing of macromolecules above Tm 14.82).…”

Section: )mentioning

confidence: 93%

Thermotropic Mesophases in Element-Organic Polymers

Godovsky

Папков

Dušek³

1989

Speciality Polymers/Polymer Physics

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This review is primarily concerned with mesomorphic behaviour of element-organic polymers, such as linear and cyclolinear polyorganosiloxanes and linear polyphosphazenes. These polymers can form thermotropic mesophases without any mesogens. Recent development in thermodynamics, kinetics, structure and morphology, elasticity and thermoelasticity and some other properties are considered. The influence of the molecular structure and molecular weight of linear macromolecules on the ability to form the mesophases and their temperature stability is discussed. The phase behaviour of cyclolinear polyorganosiloxanes is described with special emphases on the temperature stability of the mesophases as a function of molecular structure, tacticity, substituents and flexible spacers. The state of order of polyorganosiloxanes is analysed in comparison to mesophase states of linear and cyclic low molecular siloxanes. The Iyotropic mesophase behaviour of the ladder polyorganosiloxanes is also examined briefly.

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Section: )mentioning

confidence: 93%

Thermotropic Mesophases in Element-Organic Polymers

Godovsky

Папков

Dušek³

1989

Speciality Polymers/Polymer Physics

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“…Scale bars correspond to 50 nm. [20] They proposed an onconventional coalescent pathway,named growth mechanism, as the most likely pathway to lead to toroidal micelles.T his mechanism involves the presence of bicontinuous aggregates as intermediates.T hus,o ur results,t ot he best of our knowledge,s erve as the first experimental evidence of am orphological bicontinuous-to-toroid evolution triggered by the BCP concentration. Scale bar in (d) corresponds to 50 nm.…”

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confidence: 99%

“…Thesolution was aged for 24 h(without stirring) and analyzed by DLS (see Figure S8). [20] They proposed an onconventional coalescent pathway,named growth mechanism, as the most likely pathway to lead to toroidal micelles.T his mechanism involves the presence of bicontinuous aggregates as intermediates.T hus,o ur results,t ot he best of our knowledge,s erve as the first experimental evidence of am orphological bicontinuous-to-toroid evolution triggered by the BCP concentration. Both HRTEM and cryo-TEM (see Figure S2) confirmed the presence of bicontinuous nanospheres with the same structure as that obtained when 1mgof6 was dissolved in 3mLof THF.W hen the solution containing the bicontinuous nanospheres was slowly evaporated (with slow magnetic stirring under af low of N 2 (g) in ab ath at 20 8 8Ct oa void the cooling down of the solution) to reach ac oncentration of 2mgmL À1 Figure 2.…”

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confidence: 99%

“…He and Schmid demonstrated theoretically that pure toroidal micelles (i.e., exclusively with at oroidal shape) can be created by the self-assembly of as ingle component diblock copolymer (A-b-B) in the presence of as ingle solvent (S). [20] They proposed an onconventional coalescent pathway,named growth mechanism, as the most likely pathway to lead to toroidal micelles.T his mechanism involves the presence of bicontinuous aggregates as intermediates.T hus,o ur results,t ot he best of our knowledge,s erve as the first experimental evidence of am orphological bicontinuous-to-toroid evolution triggered by the BCP concentration. Moreover,they give experimental support to the theoretically predicted growth mechanism in the formation of toroidal micelles from the self-assembly of BCPs.To examine the influence of the crystallinity of the coreforming [N=P(OCH 2 CF 3 ) 2 ]blocks,weperformed wide-angle X-ray scattering (WAXS) analysis of bulk samples of block copolymers 6 (as obtained after precipitation from solutions in THF into hexanes) and dried films containing the bicontinuous nanospheres and toroidal micelles (see the Supporting Information) resulting from their self-assembly ( Figure 3).…”

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confidence: 99%

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Formation and Reversible Morphological Transition of Bicontinuous Nanospheres and Toroidal Micelles by the Self‐Assembly of a Crystalline‐b‐Coil Diblock Copolymer

2016

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We herein report the formation of two complex nanostructures,t oroidal micelles and bicontinuous nanospheres,b yt he self-assembly of the single structurally simple crystalline-b-coil diblock copolymer poly[bis(trifluoroethoxy)phosphazene]-b-poly(styrene), PTFEP-b-PS,i n one solvent (THF) and without additives.T he nature of these nanostructures in solution was confirmed by DLS and cryo-TEM experiments.The two morphologies are related by means of anew type of reversible morphological evolution, bicontinuous-to-toroidal, triggered by changes in the polymer concentration. WAXS experiments showed that the degree of crystallinity of the PTFEP chains located at the core of the toroids was higher than that in the bicontinuous nanospheres,t hus indicating that the final morphology of the aggregates is mostly determined by the ordering of the PTFEP core-forming blocks.The self-assembly of amphiphilic block copolymers (BCPs) has been demonstrated as an invaluable tool for the construction of well-defined nanostructures. [1] Besides the classical nanomorphologies created by this methodology (spheres,c ylinders,o rb ilayer membranes), [1,2] nanotoroids (donut-or ring-shaped) and bicontinuous nanospheres have become textures of special interest owing to their rarity, complexity,a nd importance in some technological and biological processes.F or instance,N ature uses nanotoroidal morphologies during DNApackaging (DNAcondensation) [3] and in some viruses and sperm cells. [4] Toroids are also very important in the design of artificial delivery systems for gene therapy. [5] On the other hand, micelles with internal bicontinuous structures are considered promising carriers for the simultaneous inclusion of chemically different encapsulated drugs and of interest for their possible catalytic and templating properties. [6] Since pioneering studies on the synthesis of toroidal [7] and bicontinuous nanostructures [8] from the selfassembly of BCPs,very few examples of toroidal (mixed with other morphologies) [9] and bicontinuous [10] micelles derived from BCPs have been reported, mostly from chemically and structurally rather complex combinations of blocks.However, these two morphologies have also been produced purely from simple linear block copolymers, [11] thus demonstrating that structural complexity is not an ecessary condition for their formation.Theself-assembly of block copolymers containing ac rystallizable core-forming block and ar andom-coil block (crystalline-b-coil BCPs) has been exploited to create complex nanomorphologies by crystallization-driven living self-assembly. [12] Recently,our group has demonstrated the synthesis of reversibly responsive (to changes in pH) giant unilamellar vesicles (GUVs) by the self-assembly of the BCPs [N = P(OCH 2 CF 3 ) 2 ] n -b-[N = PMePh] m containing crystalline [N=P(OCH 2 CF 3 ) 2 ]s egments. [13] Herein we report an ew and convenient synthesis of the hybrid crystalline-b-coil poly-[bis(trifluoroethoxy)phosphazene]-b-polystyrene (PTFEP-PS) by the use of lithiated initiators funct...

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“…The majority of publications is dedicated to the description of the mesophase state of polyfluoroalkoxyphosphazenes [7][8][9][10][11][12]. Perhaps the presence of fluorine atoms at the side branches favors the occurrence of specific interaction, leading to a stepwise melting of the crystalline structure.…”

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confidence: 99%

Mesophase State of Polyorganophosphazenes

Kulichikhin¹,

Антипов²,

Borisenkova³

et al. 1994

Partially Ordered Systems

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Earlier it was believed [1] that an ordering at a level exceeding the shortrange order of low molecular liquids cannot exist above the melting point in flexible-chain polymers which do not contain meso genic groups. However, recently, a large number of polymers, for example, polyphosphazene, has been found, which cannot be described in the framework of the traditional classification of liquid crystals. An additional type of mesomorphic state, that of a conformationally disordered crystal, was suggested [2,3].A more common approach is analyzing this type of mesophase as a threedimensional ordered crystal having a different perfection extent along each of its crystallographic dimensions. In order to gain a better insight into this problem, it is necessary to accumulate experimental evidence.Polyorganophosphazenes (PPh) with the following general formula:are of interest from the viewpoint of the meso phase class of polymers [4], since many of the representatives of this class may have an ordering level intermediate between a crystalline and an amorphous state in a broad temperature range [5]. A comprehensive review of earlier works on the structure and properties of PPh was published in [6]. The number of publications on the description of the structure, morphology, and characteristics of the physical transitions and physical-mechanical properties of these polymers has considerably increased in recent years. However, there is no complete information on the structure of PPh, especially in the mesomorphous state. V. P. Shibaev et al. (eds.), Liquid Crystalline and Mesomorphic Polymers

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Rheooptical investigation of the transition behavior of polyphosphazenes

Cited by 18 publications

References 2 publications

Thermotropic Mesophases in Element-Organic Polymers

Thermotropic Mesophases in Element-Organic Polymers

Formation and Reversible Morphological Transition of Bicontinuous Nanospheres and Toroidal Micelles by the Self‐Assembly of a Crystalline‐b‐Coil Diblock Copolymer

Mesophase State of Polyorganophosphazenes

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