Showing papers by "Harry R. Allcock published in 1999"
51 citations
TL;DR: In this article, tris(o-phenylenedioxy)cyclotriphosphazene was found to form hexagonal host−guest inclusion adducts (clathrates) with the polymers.
Abstract: Tris(o-phenylenedioxy)cyclotriphosphazene was found to form hexagonal host−guest inclusion adducts (clathrates) with the polymers: cis-1,4-polybutadiene, trans-1,4-polyisoprene, polyethylene, poly(ethylene oxide), and polytetrahydrofuran. Single-crystal X-ray diffraction studies of both the polyethylene and poly(ethylene oxide) inclusion adducts revealed the presence of individual polymer chains extended along tunnel-like voids within the host lattice. Both polyethylene and poly(ethylene oxide) were incommensurate within the tunnel-like voids preventing the exact elucidation of the polymer conformation. Average repeat unit lengths calculated for these polymers suggest that both are in an extended conformation. Both the polyethylene and poly(ethylene oxide) adducts crystallized from benzene in the space group P63/m. Inclusion adducts of the five different polymers were examined by differential scanning calorimetry (DSC) and powder X-ray diffraction. In each case, the melting point of the inclusion adduct ...
42 citations
TL;DR: Polyphosphazene single-substituent polymers were synthesized with the general formula [NP(OCH2CH2OCH 2CH2XCH3)2] where X = oxygen for polymer 5 or X = sulfur for polymer 6.
Abstract: Polyphosphazene single-substituent polymers were synthesized with the general formula [NP(OCH2CH2OCH2CH2XCH3)2] where X = oxygen for polymer 5 or X = sulfur for polymer 6. Characterization of these...
40 citations
TL;DR: In this article, a ring-opening metathesis polymerization of phosphazene-functionalized norbornenes was demonstrated with the use of (PCy3)2Cl2RuCHPh as catalyst (where Cy = cyclohexyl).
Abstract: Ring-opening metathesis polymerization (ROMP) of phosphazene-functionalized norbornenes was demonstrated with the use of (PCy3)2Cl2RuCHPh as catalyst (where Cy = cyclohexyl). This allowed the incor...
36 citations
34 citations
TL;DR: A method for the synthesis of well-defined mono-, di-, and mixed-telechelic polyphosphazenes produced via a living cationic polymerization of phosphoranimines is described.
Abstract: A method for the synthesis of well-defined mono-, di-, and mixed-telechelic polyphosphazenes produced via a living cationic polymerization of phosphoranimines is described. Amino phosphoranimines R−NH(CF3CH2O)2PNSiMe3 (R = Ph−, p-BrPh−, p-H3CPh−, CH2CHCH2−, and CH2CHPh−) were synthesized via a reaction between a bromophosphoranimine and the appropriate organic amine. Ditelechelic polymers [R−NH]2−[Cl2PN]n were prepared by quenching living poly(dichlorophosphazene) chains, [Cl3PN(Cl2PN)n−PCl3]+[PCl6]- with small quantities of the amino phosphoranimines. Cationic initiators of the amino phosphoranimines were also generated using PCl5 and were used to polymerize Cl3PNSiMe3, to give monotelechelic poly(dichlorophosphazenes). In addition, a mixed telechelic system was produced by the termination of an allylamino monotelechelic poly(dichlorophosphazene) chain with a bromoanilino phosphoranimine. In all cases, displacement of the chlorine atoms with sodium trifluoroethoxide yielded hydrolytically stable telechel...
32 citations
TL;DR: The tris(3,6-dimethylphenylenedioxy)cyclotriphosphazene−dioxane inclusion adduct was described in this paper, where the guest occupied a cagelike void located between the phosphazene rings.
Abstract: The synthesis and inclusion properties of a new clathration host, tris(3,6-dimethylphenylenedioxy)cyclotriphosphazene, is described. The guest-free structure has a triclinic unit cell, space group P1, with unit cell dimensions a = 9.418(1) A, b = 17.887(4) A, c = 8.036(2) A, α = 95.50(2)°, β = 100.57(1)°, and γ = 95.58(1)°. Recrystallization of the host from dioxane or from a poly(tetramethylene oxide)/benzene mixture afforded two different guest-included structures. The tris(3,6-dimethylphenylenedioxy)cyclotriphosphazene−dioxane inclusion adduct crystallizes in a monoclinic system, space group P21/c, with unit cell dimensions a = 9.3481(1), b = 19.6569(1), c = 16.4099(3), and β = 97.351(1)°. The guest occupies a cagelike void located between the phosphazene rings. The poly(tetramethylene oxide) adduct crystallizes in a hexagonal system, space group P63/m, with unit cell dimensions a = 11.4902(2) A and c = 13.3138(3) A. In this case, the polymeric guest is located in tunnels created along the c-axis. Add...
22 citations
TL;DR: The synthesis of phosphazene cyclic trimers with azido side groups and aryloxy, alkoxy, or dialkylamino cosubstituent groups was accomplished and the ability of these materials to undergo a reaction unique to azido compounds known as nitrene insertion was determined.
Abstract: The synthesis of phosphazene cyclic trimers with azido side groups and aryloxy, alkoxy, or dialkylamino cosubstituent groups was accomplished. The compounds have the basic structure N3P3(R)x(N3)6-x, where R represents phenoxy, trifluoroethoxy, dimethylamino, or diethylamino groups and x = 3−5. Experiments were also conducted to determine the ability of these materials to undergo a reaction unique to azido compounds known as nitrene insertion. The aryloxy derivative, N3P3(OC6H5)5(N3), yielded a nitrene insertion product when heated with 1-phenylnonane at 280 °C. The alkoxy derivative, N3P3(OCH2CF3)5(N3), produced a nitrene insertion product when ultraviolet irradiated in an aliphatic solvent. The dialkylamino derivative, N3P3(N(CH3)2)4(N3)2, did not undergo nitrene insertion. The aryloxy and alkoxy azido trimers reacted with various phosphorus(III) compounds to form phosphinimines via the Staudinger reaction. Finally, sodium phenoxide displaced azides from both the alkoxy- and aryloxyphosphazene trimers wh...
20 citations
TL;DR: In this article, an improved synthesis of the phosphazene polymerization precursors, hexachlorocyclotriphosphazene, (NPCl2)3 (1), and Cl3PNSiMe3 (2), was reported.
Abstract: An improved synthesis of the phosphazene polymerization precursors, hexachlorocyclotriphosphazene, (NPCl2)3 (1), and Cl3PNSiMe3 (2) is reported. The addition of PCl5 to N(SiMe3)3 in methylene chloride at 40 °C produced a mixture of phosphazenes which contained 76% of 1. However, the addition of N(SiMe3)3 to PCl5 in methylene chloride at 0 °C, followed by the addition of hexane, provided 2 in 40% yield. The mechanism of the reaction is discussed.
20 citations
TL;DR: In this paper, a new polyphosphazene, [N=PPh(CF 3 )] n, has been prepared via the PCl 5 -induced cationic polymerization of Me 3 SiN =P(CF3 )(Ph)Br, which failed to polymerize under any conditions but was used as an initiator and terminator to prepare both mono- and ditelechelic polymers.
Abstract: A new polyphosphazene, [N=PPh(CF 3 )] n , has been prepared via the PCl 5 -induced cationic polymerization of Me 3 SiN=P(CF 3 )(Ph)Br. In addition, the cationic route has been used to produce [N= PPh(Me)] n with controlled molecular weights and narrow polydispersities. By contrast, the new monomer Me 3 SiN=P(t-Bu)(Ph)F failed to polymerize under any conditions but was used as an initiator and terminator to prepare both mono- and ditelechelic polymers. This monomer was also used to prepare [F(Ph)(t-Bu)P=N(PCl 2 =N)P(t-Bu)(Ph)F] + , which was used as a substrate for reactions with alkoxy and aryloxy groups to yield the hydrolytically stable materials, [R(Ph)(t-Bu)P=N(PR 2 =N)P(t-Bu)(Ph)R 2 ].
8 citations
Patent•
16 Jun 1999TL;DR: Incorporation of phosphate and phosphonate units into the side groups of aryloxyphosphazenes, at both the polymer and cyclic trimer levels, is disclosed as mentioned in this paper.
Abstract: Incorporation of phosphate and phosphonate units into the side groups of aryloxyphosphazenes, at both the polymer and cyclic trimer levels, is disclosed Phosphorylated cyclic trimers are utilized as flame-retardant additives to polystyrene
TL;DR: In this article, a new method for the synthesis of polyphosphazenes is described, together with the biomedical and electrochemical uses of phosphazene polymers with alkyl ether side groups.
Abstract: A new method for the synthesis of polyphosphazenes is described, together with the biomedical and electrochemical uses of phosphazene polymers with alkyl ether side groups
TL;DR: In this paper, an improved synthesis of the phosphazene polymerization precursors, hexachlorocyclotriphosphazene, (NPCl2)3 (1), and Cl3PNSiMe3 (2), was reported.
Abstract: An improved synthesis of the phosphazene polymerization precursors, hexachlorocyclotriphosphazene, (NPCl2)3 (1), and Cl3PNSiMe3 (2) is reported. The addition of PCl5 to N(SiMe3)3 in methylene chloride at 40 °C produced a mixture of phosphazenes which contained 76% of 1. However, the addition of N(SiMe3)3 to PCl5 in methylene chloride at 0 °C, followed by the addition of hexane, provided 2 in 40% yield. The mechanism of the reaction is discussed.
Journal Article•
Journal Article•
Journal Article•
TL;DR: In this paper, protectiondeprotection reactions and direct reactions of active reagents with the organic side-groups of non-functional poly(organophosphazenes) have been applied both at molecular level and in the form of reactions carried out only at polymer surfaces.
Abstract: The macromolecular substitution approach for the synthesis of polyphosphazenes provides access to many different polymers. However, it precludes the use of reagents that contain two or more functional groups because such compounds would cause extensive crosslinking of the chains. This presents a problem because many of the uses for which polyphosphazenes seem ideally suited require the presence of -OH, -COOH, -NH2, -SO3H, -PR2 and other functional units in the side-chain structure. We have developed two approaches to introduce such active sites: (1) protection‐deprotection reactions; and (2) direct reactions of active reagents with the organic side-groups of non-functional poly(organophosphazenes). These methods have been applied both at the molecular level and in the form of reactions carried out only at polymer surfaces. The resultant polymers have special properties that are valuable in the microencapsulation of sensitive biological agents; in the formation of hydrophobic, hydrophilic, or adhesive surfaces; in crosslinking reactions; and in the development of solid polymer electrolytes, bio-erodible polymers, pH-triggered hydrogels, polymer blends and interpenetrating polymer networks. Overall, more than 700 different polyphosphazenes are now known, and a large number of these are functional macromolecules targeted for specific property combinations and uses. # 1998 John Wiley & Sons, Ltd.