Transition diagrams for a liquid crystalline thermoset containing a rigid-rod epoxy

2006 ◽  
Vol 46 (5) ◽  
pp. 623-629 ◽  
Author(s):  
Seunghyun Cho ◽  
Elliot P. Douglas ◽  
Jun Young Lee
Keyword(s):  
Liquid Crystalline ◽  
Rigid Rod ◽  
Liquid Crystalline Thermoset

Activation Energies of Liquid Crystalline Thermoset Containing Rigid-Rod Epoxy

2011 ◽  
Vol 378-379 ◽  
pp. 628-631 ◽  
Author(s):  
Seung Hwan Byun ◽  
Seung Hyun Cho
Keyword(s):  
Differential Scanning Calorimetry ◽  
Weight Loss ◽  
Thermogravimetric Analysis ◽  
Liquid Crystalline ◽  
Activation Energies ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Rigid Rod ◽  
Liquid Crystalline Thermoset ◽  
Weight Loss Process

4,4’-Diglycidyloxy-α-methylstilbene (DOMS) was synthesized and characterized with cross-polarized optical microscopy (POM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Activation energies for decomposition (Ed) by TGA were determined as a function of conversion by weight loss process.

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.

Permeability of A Liquid Crystalline Epoxy

2001 ◽  
Vol 709 ◽  
Author(s):  
Jianxun Feng ◽  
Elliot P. Douglas
Keyword(s):  
Liquid Crystalline ◽  
Barrier Properties ◽  
Two Phase ◽  
Solubility Coefficient ◽  
Epoxy Network ◽  
Liquid Crystalline Epoxy ◽  
Smectic Mesophase ◽  
Liquid Crystalline Thermoset ◽  
Epoxy Systems ◽  
Main Factor

ABSTRACTThis paper presents a comparison of moisture permeation in liquid crystalline and conventional epoxy systems. The permeability is obtained using a dynamic method. It is found that both epoxy systems exhibit Fickian behavior. The liquid crystalline epoxy network exhibits higher barrier properties for moisture transport than the conventional epoxy network. The efficient chain packing within the smectic mesophase of the liquid crystalline thermoset (LCT) is suggested as the main factor for this difference. The stoichiometry has a large effect on the moisture permeation. The diffusion coefficient decreases monotonically with increasing amine/epoxide functional ratio. The permeability (P) and solubility coefficient (S) reach a minimum at a functional ratio of one. The mechanism of the permeation is described in terms of the two-phase morphology present and hydrogen bonding between absorbed water and the network.

Organo-Soluble Polyimides: Synthesis and Characterization of Polyimides Containing Phenylated p-Biphenyl and p-Terphenyl Units

1997 ◽  
Vol 9 (3) ◽  
pp. 251-261 ◽  
Author(s):  
Frank W Harris ◽  
Yoshimitsu Sakaguchi ◽  
Mitsuhiro Shibata ◽  
Stephen Z D Cheng
Keyword(s):  
Sulphuric Acid ◽  
Liquid Crystalline ◽  
Chlorinated Solvents ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Weight Losses ◽  
Flexible Films ◽  
Solution Cast ◽  
Rigid Rod ◽  
Biphenyltetracarboxylic Dianhydride

4, 4′-diamino-2, 2′-diphenylbiphenyl (1), 4,4″-diamino-2′, 3′, 5′-triphenyl- p-terphenyl (2a) and 4,4″-diamino-2′, 3′, 5′, 6′-tetraphenyl- p-terphenyl (2b) have been polymerized with several aromatic dianhydrides in refluxing m-cresol containing isoquinoline to afford a series of phenylated polyimides. The polymerization mixtures of 1 and 3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA) and 3, 3′4, 4′-benzophenonetetracarboxylic dianhydride (BTDA) and of 2a and pyromellitic dianhydride (PMDA) set to gel-like structures upon cooling. The gels, which displayed optical anisotropy typical of a liquid crystalline-like phase, could be dissolved by heating and re-formed by cooling. Although the p-catenated, rigid-rod polymers obtained from the diamines and PMDA were only soluble in concentrated sulphuric acid, the polymers that were prepared from 1 and 2a and 3, 3′, 4, 4′-diphenylethertetracarboxylic dianhydride (ODPA), 3, 3′, 4, 4′-diphenylsulphonetetracarboxylic dianhydride (DSDA) and 2, 2-bis[4-(1, 2-dicarboxyphenyl)]-1, 1, 1, 3, 3, 3-hexafluoropropane dianhydride (6FDA) were soluble in N-methyl-2-pyrrolidinone (NMP), m-cresol and chlorinated solvents. In general, polymers prepared from 2a were the most soluble, while polymers prepared from 2b were the least soluble. The intrinsic viscosities of the polymers ranged from ′.61 to 5.1 dl g−1 in concentrated sulphuric acid or NMP at 3′°C. The glass transition temperatures of most of the polymers could not be detected with differential scanning calorimetry. The temperatures at which the polymers underwent 5% weight losses when subjected to thermal gravimetric analysis ranged from 5″ to 6′°C in both air and nitrogen. Several of the polymers could be solution cast into thin, water-white flexible films.

Isothermal Curing of Acetylene Functionalized Liquid Crystalline Thermoset Monomers

2001 ◽  
Vol 34 (17) ◽  
pp. 5876-5884 ◽  
Author(s):  
Arthur J. Gavrin ◽  
Elliot P. Douglas
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Thermoset
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