Acetylene-terminated polymers

In the energy domain, new and efficient uses in gas lines, electric cable ducts and the like, will promote surface stabilization and endurance as well as complex stress capability of various extruded or cast systems. Such reactants as acetylene terminated polymers have yielded cross-linked cured, networks of exceptional density and durability. A diimide dianhydride combined with (3) ethynylaniline yields an acetylene terminated tetraimide. On further polymerization at 250°C, the cross-linked structure derived can be used continuously at about 230°C. When this is combined with polymer carbon fibers or filaments, an exceedingly refractory and tough binder is produced. 

Many engineering thermoplastics (e.g., polysulfone, polycarbonate, etc.) have limited utility in applications that require exposure to chemical environments. Environmental stress cracking [13] occurs when a stressed polymer is exposed to solvents. Poly(aryl ether phenylquin-oxalines) [27] and poly(aryl ether benzoxazoles) [60] show poor resistance to environmental stress cracking in the presence of acetone, chloroform, etc. This is expected because these structures are amorphous, and there is no crystallinity or liquid crystalline type structure to give solvent resistance. Thus, these materials may have limited utility in processes or applications that require multiple solvent coatings or exposures, whereas acetylene terminated polyaryl ethers [13] exhibit excellent processability, high adhesive properties, and good resistance to hydraulic fluid. 

To improve the processability of PPQ, appropriate phenylquinox-aline oligomers were end-capped with acetylenic groups using 3-(3,4-diaminophenoxy)phenylacetylene (43) or 4-(3- and 4-ethynyl-phenoxy)benzil (44, 45) (Eq. 10). The processability was improved but at the sacrifice of the thermooxidative stability. In general, cured acetylene-terminated heterocyclic polymers are less stable in a thermooxidative environment than the parent linear polymer. 

Solid state NMR has been used to study polymers of various classes over the past several years. In particular, the technique has been used to study curing reactions in epoxies (12). polyimides (1), and acetylenic terminated sulfones (13). The ability to observe the evolution of the carbons of the reacting species has been clearly shown to provide valuable information which has been difficult or impossible to obtain with other techniques. The use of 13C solid state NMR techniques is essential for the understanding of curing reactions in high temperature polymers in order to be able to correlate the reaction chemistry with the structural and resulting physical properties. 

The objectives of this study were to extend these synthetic methods to the preparation of low molecular weight, hydroxy-terminated polymers containing acetylenic bonds and evaluating these prepolymers in castable solid propellant formulations. Since 2-butyne-l,4-diol was commercially available, the formation of polyacetals from this glycol seemed to be an attractive route to the desired polymers. It was believed that the rigid triple bond would inhibit the cyclic acetal formation observed by the earlier workers with the lower members of the saturated glycol series. Thus, in an acetal interchange reaction a linear polymer (I) should be favored over the cyclic acetal (II) ... 

A family of acetylene-terminated phenyl quinoxalines have been synthesized by the Polymer Branch of the Materials Laboratory. ( 1) These phenyl quinoxalines are remarkable for their thermooxidative stability and resistance to moisture. These materials have potential for structural applications as adhesives or composite matrix resins.(2) The feature of moisture resistance makes the materials especially attractive for bonding aluminum. However, problems arise from the fact that aircraft aluminum alloys (and their surface oxiges) are altered by exposures to temperatures above 177 C (350 F) and this is much lower than the polymerization temperatures of the acetylene-terminated oligomers. 

The c/s-dihydroxylation reaction catalyzed by these dioxygenases is typically highly enantioselective (often >98% ee) and, as a result, has proven particularly useful as a source of chiral synthetic intermediates (2,4). Chiral cis-dihydrodiols have been made available commercially and a practical laboratory procedure for the oxidation of chlorobenzene to IS, 2S)-3-chlorocyclohexa-3,5-diene-l,2-c diol by a mutant strain of Pseudomonas putida has been published (6). Transformation with whole cells can be achieved either by mutant strains that lack the second enzyme in the aromatic catabolic pathway, cw-dihydrodiol dehydrogenase (E.C. 1.3.1.19), or by recombinant strains expressing the cloned dioxygenase. This biocatalytic process is scalable, and has been used to synthesize polymer precursors such as 3-hydroxyphenylacetylene, an intermediate in the production of acetylene-terminated resins (7). A synthesis of polyphenylene was developed by ICI whereby ftie product of enzymatic benzene dioxygenation, c/s-cyclohexa-3,5-diene-1,2-diol, was acetylated and polymerized as shown in Scheme 2 (8). 

The gas permeation parameters have also been reported for polymers obtained via ether reaction of epoxy and diamines [57,58], for polymer blends with acetylene-terminated oligomer [73,74] and internal acetylene polyimide [72,75]. The gas permeability of cross-linked internal acetylene-containing polymer, 6FDA-TeMPD/p-intA (4 1) declines from 612 to 186Barrer, while the selectivity, a(C02/CH4) increases from 14 to 25 at 35°C and lOatm [75]. Moreover, this cross-linked 6FDA-TeMPD/p-intA (4 1) membrane is still stable under CO2 pressure of about 47 atm. 

Polyphenylquinoxalines (PPQ s) were first prepared in 1967 by Hergenrother (56). In 1975, Koval et al. (57,58) introduced the acetylene-terminated PPQ (ATPQ) (Pig. 10), which is the addition type of PPQ. Resembling ATPI, ATPQ also has shortcomings. The ethynl group hinders the flow of the polymer chain, and the cured ATPQ is less thermal-oxidatively stable than the comparable PPQ. The detailed status of PPQ, as well as other high-temperature adhesives, is discussed by Hergenrother (45). ... 

Addition Cured Acetylene Terminated Polyphenylquin-oxaline Oligomers," Polym. Chem. Preprints, 21,... 

Reactions of Hydrocarbons. Several types of reactive hydrocarbon functional groups can be used to polymerize and cross-Unk monomers and ohgomers into thermoset plastics. These include addition polymerization of acetylene-terminated molecules and ring-opening polymerization of strained carbon rings. They also include Friedel-Crafts condensation to form hydrocarbon polymers. 

Polysulfones have been made from acetylene-terminated sulfone monomers (Fig. 3.51), and cured graphite-fiber laminates have shown Tg = 300°C and good mechanical properties at 170°C before and after heat and humid aging. Semi-interpenetrating polymer networks with linear thermoplastic polysulfones showed promise of combining the heat deflection temperature and solvent-resistance of the thermoset polymer with the impact resistance of the thermoplastic. 

Figure 12.8 Schematic representation of (a) step-growth coupling of bivalent azide and bivalent acetylene telechelic polymers (b) polymer modi cation by CuAAC of pendant alkyne groups of polymers, e.g., poly(vinyl acetylene), with an azide-bearing substrate and (c) functionalization of polymer by CuAAC of pendant azide with alkyne-bearing functional moiety. Azide terminated dendrimers are similarly subjected to CuAAC with alkyne-derivatized functional moieties to achieve desired functionalization of dendritic macromolecules.

Several papers have appeared describing water permeation, electrical conductivity, cross-linking efficiency of curing polymers, and the kinetics of sulphur dioxide sorption in polyimides. Carbon-13 n.m.r., has been used to examine acetylene-terminated polyimides. ... 

M. R. Uhroe and F. L. Hedberg, "A Novel Low-Cost Route to Acetylene Terminated Resins." Polym. Prepr.. 23 189 (1982). 

FIGURE 26.22 Phenyl acetylene-terminated poly(carborane-silane) (PACS) polymer. 

Quan, Z. Zuju, M. Lizhong, N. Jianding, C. 2007. Novel phenyl acetylene terminated poly(carborane-silane) Synthesis, characterization, and thermal property. J. Appl. Polym. ScL, 104 2498-2503. 

Diacetylenes in phospholipid bilayers have been the subject of extensive studies in our laboratory, not only because of the highly conjugated polymers they form, but also because of their ability to transform bilayers into interesting microstructures. Consequent to our synthesis and characterization of several isomeric diacetylenic phospholipids, we have found that the polymerization in diacetylenic bilayers is not complete. In order to achieve participation of all diacetylenic lipid monomer in the polymerization process, diacetylenic phospholipid was mixed with a spacer lipid, which contained similar number of methylenes as were between the ester linkage and the diacetylene of the polymerizable lipid. Depending upon the composition of the mixtures different morphologies, ranging from tubules to liposomes, have been observed. Polymerization efficiency has been found to be dependent on the composition of the two lipids and in all cases the polymerization was more rapid and efficient than the pure diacetylenic system. We present the results on the polymerization properties of the diacetylenic phosphatidylcholines in the presence of a spacer lipid which is an acetylene-terminated phosphatidylcholine. 

Azido-terminated polymers can also be used in dick chemistry modifications with acetylene derivatives to incorporate various functional groups. Polymers with phosphonium end-groups were prepared from bromine-terminated PS or polyacrylates and BusP. Mercapto-terminated PS was prepared by the reaction of the corresponding bromo-compound with either thiodimethylformamide or thiourea followed by reaction with a nucleophile. ... 

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