Electron microscopy of a triblock copolymer molecular composite

1986 ◽  
Vol 44 ◽  
pp. 790-791
Author(s):  
T. Haddock ◽  
S. J. Krause ◽  
W. W. Adams
Keyword(s):  
Triblock Copolymer ◽  
Critical Factor ◽  
High Strength ◽  
Fiber Spinning ◽  
Chain Polymer ◽  
The Matrix ◽  
Molecular Composites ◽  
Polymer Component ◽  
Flexible Coil ◽  
Rigid Rod

Molecular composites are a new class of structural polymers which are high-strength, high-modulus, thermally stable, and environmentally resistant. A rigid-rod, extended chain polymer component is used to reinforce a matrix of flexible, coil-like polymer component with the intent of achieving a composite on the molecular level. The critical factor in processing a molecular composite is that the rod-like reinforcing component be well dispersed and not phase separate from the matrix component. We previously reported on the morphology of a molecular composite from a physical blend of rigid-rod and flexible-coil homopolymers. In this paper we are reporting on the morphology of a rigid-rod, flexible-coil, triblock copolymer processed by vacuum casting or fiber spinning from a dilute solution.

Electron microscopy of rod/coil molecular composites

1983 ◽  
Vol 41 ◽  
pp. 32-33
Author(s):  
S. J. Krause ◽  
W. W. Adams
Keyword(s):  
Critical Factor ◽  
High Strength ◽  
Chain Polymer ◽  
New Class ◽  
Reinforced Composite ◽  
Transmission Electron ◽  
The Matrix ◽  
Molecular Composites ◽  
Flexible Coil ◽  
Rigid Rod

Molecular composites are a new class of structural polymers which are lightweight, high-strength, high-modulus, and environmentally resistant. A rigid-rod, extended chain, polymer is used to reinforce a matrix of flexible, coil-like polymer with the intent of achieving a composite on the molecular level which is analagous to a macroscopic chopped-fiber reinforced composite. The critical factor in making a molecular composite is that the rod-like reinforcing molecules be well dispersed and not phase separate from the matrix polymer to insure that the aspect ratio (ratio of length to width) of the reinforcing phase has a high value. This paper reports the first transmission electron microsopy (TEM) study of phase separation in molecular composites.

Electron microscopy of a rigid-rod/nylon thermoplastic molecular composite physical blend

1988 ◽  
Vol 46 ◽  
pp. 748-749
Author(s):  
P. Lloyd ◽  
R. Omlor ◽  
D. Vezie ◽  
S. J. Krause ◽  
S. Kumar ◽  
...  
Keyword(s):  
Critical Factor ◽  
High Strength ◽  
Chain Polymer ◽  
Degradation Temperature ◽  
The Matrix ◽  
Molecular Composites ◽  
Ductile Polymer ◽  
Flexible Coil ◽  
Rigid Rod ◽  
Processing Techniques

“Molecular composites” are a new class of structural polymers which are high-strength, high-modulus, thermally stable, and environmentally resistant. A rigid-rod, extended chain polymer component is used to reinforce a matrix of a ductile polymer with the intent of achieving a composite on the molecular level. The critical factor in processing a “molecular composites” is that the rigid-rod reinforcing component be well dispersed and not phase separate from the matrix component at any stage of processing. For the greatest versatility, a “molecular composites” system should be amenable to fabrication with traditional thermoplastic processing techniques. We previously reported on the morphology of “molecular composites” formed by coagulation spinning from a solution of rigid-rod/stiff-coil polymer blend and from a solution of a rigid-rod/stiff-coil triblock copolymer. Although these polymer systems formed “molecular composites”, they did not have a glass transition temperature below the degradation temperature and could not be consolidated by thermal processing techniques. In this paper we are reporting on the morphology of rigid-rod and flexible-coil thermoplastic blends which are processable by precipitation and thermal consolidation.

Morphology of High-Performance Rigid-Rod Polymer Fibers and Molecular Composites

1989 ◽  
Vol 47 ◽  
pp. 338-339
Author(s):  
W.W. Adams ◽  
S. J. Krause
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Liquid Crystalline ◽  
Molecular Level ◽  
Synergistic Effects ◽  
Tensile Modulus ◽  
Commercial Development ◽  
The Matrix ◽  
Molecular Composites ◽  
Rigid Rod

Rigid-rod polymers such as PBO, poly(paraphenylene benzobisoxazole), Figure 1a, are now in commercial development for use as high-performance fibers and for reinforcement at the molecular level in molecular composites. Spinning of liquid crystalline polyphosphoric acid solutions of PBO, followed by washing, drying, and tension heat treatment produces fibers which have the following properties: density of 1.59 g/cm3; tensile strength of 820 kpsi; tensile modulus of 52 Mpsi; compressive strength of 50 kpsi; they are electrically insulating; they do not absorb moisture; and they are insensitive to radiation, including ultraviolet. Since the chain modulus of PBO is estimated to be 730 GPa, the high stiffness also affords the opportunity to reinforce a flexible coil polymer at the molecular level, in analogy to a chopped fiber reinforced composite. The objectives of the molecular composite concept are to eliminate the thermal expansion coefficient mismatch between the fiber and the matrix, as occurs in conventional composites, to eliminate the interface between the fiber and the matrix, and, hopefully, to obtain synergistic effects from the exceptional stiffness of the rigid-rod molecule. These expectations have been confirmed in the case of blending rigid-rod PBZT, poly(paraphenylene benzobisthiazole), Figure 1b, with stiff-chain ABPBI, poly 2,5(6) benzimidazole, Fig. 1c A film with 30% PBZT/70% ABPBI had tensile strength 190 kpsi and tensile modulus of 13 Mpsi when solution spun from a 3% methane sulfonic acid solution into a film. The modulus, as predicted by rule of mixtures, for a film with this composition and with planar isotropic orientation, should be 16 Mpsi. The experimental value is 80% of the theoretical value indicating that the concept of a molecular composite is valid.

Morphology of Rigid-Rod Molecular Composites: An Overview

1988 ◽  
Vol 134 ◽  
Author(s):  
Stephen J. Krause
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Morphological Characterization ◽  
High Ratio ◽  
Structure Property ◽  
Chain Polymer ◽  
Specific Strength ◽  
Composite Systems ◽  
Molecular Composites ◽  
Rigid Rod

ABSTRACTRigid-rod molecular composites are a new class of high performance structural polymers which have high specific strength and modulus and also high thermal and environmental resistance. A rigid-rod, extended chain polymer component is used to reinforce a matrix of a ductile polymer with the intent of achieving a “composite” on the molecular level. After synthesis, the key to producing a molecular composite is to control morphology to disperse the reinforcing rod molecules as finely as possible in the matrix polymer. Individual rod molecules or bundles of molecular rods must have dimensions which result in a high ratio of length to width (aspect ratio) for efficient reinforcement. To achieve this, the reinforcing rod component must not phase separate at any stage of processing. Morphological characterization techniques, which can measure the orientation and dispersion (or, conversely, the degree of phase separation) of rod molecules provide the tools for correlating theoretically predicted and experimentally observed mechanical properties. Various morphological techniques which have been applied to molecular composite systems will be reviewed, including wide angle x-ray scattering and scanning and transmission electron microscopy. Structure-property correlations for molecular composite systems will be discussed with regard to models for mechanical properties. Application of new morphological techniques will also be discussed.

Recent Advances in Morphology and Mechanical Properties of Rigid-Rod Molecular Composites

1989 ◽  
Vol 171 ◽  
Author(s):  
Stephen J. Krause ◽  
Wen-Fang Hwang
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Low Voltage ◽  
Orientation Distribution ◽  
Short Fiber ◽  
Chain Polymer ◽  
Structural Applications ◽  
Molecular Composites ◽  
Rigid Rod ◽  
Aromatic Heterocyclic

ABSTRACTRigid-rod molecular composites are a new class of high performance structural polymers which have high specific strength and modulus and also high thermal and environmental resistance. The concept of using a rigid-rod, extended chain polymer to reinforce a ductile polymer matrix at the molecular level has been demonstrated with morphological and mechanical property studies for aromatic heterocyclic systems, but new materials systems and processing techniques will be required to produce thermoplastic or thermoset molecular composites. Improved characterization and modeling will also be required. In this regard, new results on modeling of mechanical properties of molecular composites are presented and compared with experimental results. The Halpin-Tsai equations from ‘shear-lag’ theory of short fiber composites predict properties reasonably well when using the theoretical modulus of rigid-rod molecules in aromatic heterocyclic systems, but newer matrix systems will require consideration of matrix stiffness, desired rod aspect ratio, and rod orientation distribution. Application of traditional and newer morphological characterization techniques are discussed. The newer techniques include: Raman light scattering, high resolution and low voltage SEM, parallel EELS in TEM, synchrotron radiation in X-ray scattering, and ultrasound for integrity studies. The properties of molecular composites and macroscopic composites are compared and it is found that excellent potential exists for use of molecular composites in structural applications including engineering plastics, composite matrix resins, and as direct substitutes for fiber reinforced composites.

scholarly journals Giant tubular and toroidal vesicles from self-assembled triblock copolymer–polyaniline complexes in water

2015 ◽  
Vol 51 (55) ◽  
pp. 11100-11103 ◽  
Author(s):  
Anbazhagan Palanisamy ◽  
Qipeng Guo
Keyword(s):  
Triblock Copolymer ◽  
Flexible Coil ◽  
Rigid Rod ◽  
Assembled Complexes ◽  
Self Assembled

We report here a facile method for fabrication of giant tubular and toroidal vesicles from self-assembled complexes of a flexible coil-like triblock copolymer and a rigid rod conjugated homopolymer.

Preparation and Third-Order Nonlinear Optical Properties of Host-Guest Molecular Composites

1992 ◽  
Vol 277 ◽  
Author(s):  
Samson A. Jenekhe ◽  
Michael F. Roberts ◽  
Jeffrey S. Meth ◽  
Herman Vanherzeele
Keyword(s):  
Optical Properties ◽  
Nonlinear Optical ◽  
Nonlinear Optical Properties ◽  
Nylon 66 ◽  
The Matrix ◽  
Molecular Composites ◽  
Important Approach ◽  
Ladder Polymers ◽  
Rigid Rod ◽  
Linear And Nonlinear

ABSTRACTHost-guest molecular composites of conjugated rigid-rod polymers in the matrix of flexible-chain polymers were prepared from blend solutions of the Lewis acid complexes of the component polymers. Molecular composites of poly(p-phenylene benzobisthiazole) (PBZT) with the polyamides Nylon 66 and PTMHT were prepared and their linear and nonlinear optical properties were investigated by optical absorption and third harmonic generation spectroscopy, respectively. Dispersion of PBZT in a polyamide matrix was found to result in reduced π-electron interactions as evidenced by the narrowing of the main absorption band. The χ(3) spectra of composites were measured in the wavelength range 0.8–2.4μm which spans the resonant and nonresonant regions. Nonresonant χ(3) at 1.9μtm was studied as a function of composite composition and linear and nonlinear dependences of χ(3) with mole fraction of PBZT were observed for nylon 66 and PTMHT composites respectively. Our findings that both χ(3) and χ(3)/α can be enhanced in molecular composites suggest that this is an important approach to optimize materials for nonlinear optics. Preliminary results of our studies of other new molecular composites of rigid-rod and ladder polymers are also discussed.

Concept and Overview of Rigid Rod Molecular Composites

1988 ◽  
Vol 134 ◽  
Author(s):  
Wen-Fang Hwang ◽  
T. E. Helminiak
Keyword(s):  
Matrix Material ◽  
Extreme Environments ◽  
Material Technology ◽  
Thermal Expansion Coefficients ◽  
Aspect Ratios ◽  
Rigid Rods ◽  
The Matrix ◽  
Molecular Composites ◽  
Rigid Rod ◽  
New Generation

Recently, the concept of rigid rod molecular composites, originally demonstrated in the Air Force Materials Laboratory, has attracted wide spread attention in the global research community in the hope of creating a new generation of materials for structural and electronic applications in extreme environments. As originally conceived, a molecular composite is a homogeneous, synergistic composite of molecularly dispersed rigid rod polymer molecules (single molecules or small bundles of molecules with a lateral dimension of less than 50 Å) with high aspect ratios in a matrix material. The enhanced and desirable properties, such as superior chemical and environmental resistance, enhanced thermal and thermoxidative stability, toughness, and dimensional stability, resulting from the synergism between the reinforcing rigid rods and the matrix can only be realized in a true molecular composite. Without the development of true rigid rod molecular composite technology, the fundamental detrimental interfacial problems (adhesion, different thermal expansion coefficients, etc.) encountered in conventional fiber composites can not be averted. A truly revolutionary material technology can be developed only if one adheres to the original concept.

The Dynamics of Phase Separation in Rigid-Rod Molecular Composites

1988 ◽  
Vol 134 ◽  
Author(s):  
Hoe Hin Chuah ◽  
Thein Kyu ◽  
T. E. Helminiak
Keyword(s):  
Phase Separation ◽  
Main Beam ◽  
Thermally Induced Phase Separation ◽  
Thermally Induced ◽  
Universal Scaling ◽  
Dimensional Diffusion ◽  
Molecular Composites ◽  
Flexible Coil ◽  
Rigid Rod ◽  
Small Angle Light Scattering

ABSTRACTThe thermally induced phase separation of poly(p-phenylene benzobisthiazole)/ Nylon 66 molecular composites was followed by small-angle light scattering which showed the development of a scattering ring. The intensity increased and the ring moved towards the main beam as a function of time.The scattering vector qm and intensity maxima Im scaled as qm~t−∝ and Im~tβ with ∝~ 0.33 and β = 0.91-0.95, in close agreement with the cluster dynamics prediction of Binder. However, at longer times, the increase in both qm and Im slowed down dramatically indicating a different mechanism. The structure function S(x) was used to test the validity of universal scaling for a rigid-rod/flexible coil polymer blend. At large x, S(x) scaled to the power of −2.4 in x, which is in between values predicted for systems with one and two-dimensional diffusion.

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