Ionic naphthalene thermotropic polymers (NTP) based on wholly aromatic (main chain liquid crystalline) copolyesters were prepared, in which ionic monomer was introduced in the form of sodium 5-sulfoisophthalate. This meta-linked monomer introduces ionic groups as well as “kinked” units into polymer chains. A fiber-forming molecular weight was achieved for all the ionic NTP. The melt of ionic NTP showed extensive birefringence, and the majority of them exhibited nematic mesophase textures over a wide temperature range, without showing a transition to an isotropic phase at least up to 380 °C. The melting temperature (T m) and the crystallization temperature (T c) of the ionic NTP are both decreased substantially with an increase in ion-containing monomer content because of an increase of the number of “kinked” units. A unique glass transition behavior is also observed:  at the ionic content of less than 10 mol %, the glass transition temperature (T g) is rather constant, the T g value jumps when the ionic content reaches 15 mol %, and two distinct T g's with ca. a 40 deg separation are observed at 20 mol % ionic content. This seems to arise from the competition between two opposing factors:  one is a reduction of the rigidity of backbone chains by “kinked” units, which leads to lower T g, and another is intermolecular ionic interactions between chains, which lead to higher T g. Fracture surfaces of the ionic NTP fibers indicate suppression of spontaneous fibrillation with an increase of ionic content. This is an indication of decreased rigidity of the backbone chains and increased cohesion through ionic interactions between the polymer chains. Also, flat fracture surfaces observed for the high ionic content NTP fibers reflect their brittleness, arising from easier crack propagation.

Novel ionic naphthalene thermotropic polymers (NTPs), based on wholly aromatic copolyesters, were synthesized, and their tensile mechanical properties were investigated. These ionic NTPs, containing 1 mol % ionic groups with divalent metal counterions (Ba, Ca, Mg, and Zn), exhibited thermotropic liquid crystallinity. Among them, the Ca salt NTP maintained a high molecular weight and exhibited excellent thermal and mechanical properties. Systematic comparison was made among nonionic NTP, ionic NTP (Na salt), and ionic NTP (Ca salt), since they possessed similar molecular weights and since their film specimens were made under similar processing conditions. Ionic NTP with monovalent Na ions showed a moderate increase in tensile modulus and strength over nonionic NTP. However, ionic NTP with divalent Ca ions showed a significant increase:  i.e., 76% increase in modulus and 147% increase in strength. An increase in tensile properties arises from enhanced lateral support, via ionic bonds (cross-links), between highly aligned NTP chains. Ionic cross-links can effectively enhance tensile properties of the LCPs, unlike covalent cross-links, which are less effective. This arises from the nondirectional nature of ionic bonds, which makes the bonds thermally labile; thus chains aligned under elongational flow at high processing temperature are reinforced effectively upon cooling. Tensile fracture surface morphologies of ionic NTPs were also investigated as a function of counterion.

A hybrid inorganic/organic interpenetrating polymer network (IPN) of a three-dimensional network structure zeolite crystal (13X, powder) and crosslinked or linear polystyrene (PS) was prepared and characterized by differential scanning calorimetry (DSC), solid-state 13C-NMR, and scanning electron microscopy (SEM). The size and shape of the crystalline zeolite particles were revealed on SEM micrographs in both the pure zeolite and the IPNs. Solubility tests and the results of DSC with solid-state 13C-NMR confirm that some organic PS chains are incorporated within the internal three-dimensional channels of the zeolite particles. We speculate that the internal PS chains may adopt an extended "one-dimensional" conformation and exhibit no bulk polymer glass transition. These novel hybrid inorganic/organic IPNs are a new kind of IPN structure. 0

Free radical polymerization of liquid ethylacrylate in the presence of zeolite 13X yielded PIPNs without crosslinker and IPNs if the crosslinker ethylene glycol dimethacrylate was present. We studied these materials both unextracted as well as partially extracted with a variety of solvents using DSC, SEM as well as Small Angle X‐ray Scattering (SAXS). These studies suggest that in the composites polyethylacrylate chains entered the internal pores of the zeolite. These chains had an extended state and did not exhibit a bulk glass transition, a similar behavior to that previously reported for polystyrene/zeolite 13X composite. © 1996 John Wiley & Sons, Inc.