Roger De Jaeger

Poly(organophosphazene)s and related compounds: Synthesis, properties and applications

Abstract This paper presents an overview of the synthetic procedures used for the preparation of phosphazene compounds. The main reactions used in this field i.e. ring-opening polymerizations, polycondensations and free-radical processes, have been critically reviewed and the possibility of controlling these reactions by using catalysts or inhibitors evaluated. Both low-molecular-weight linear and cyclic phosphazene oligomers and high-molecular-weight phosphazene polymers have been considered.

Aspects of Phosphazene Research

This review reports research carried out by the authors during the last 10 years. The research involves the synthesis, characterization, functionalization, and possible utilization of cyclo- and polyphosphazenes. The investigations concern the synthesis of poly(dichlorophosphazene) by polycondensation reaction of dichlorophinoyliminotrichlorophosphorane; the grafting of unsaturated organic substrates (maleic anhydride, maleates or vinyl polymers) onto poly(organophosphazenes) by free radical reactions and the use of the synthesized materials for the preparation of new grafted copolymers or for the superficial modification of conventional organic macromolecules; the synthesis of phosphazenes containing free hydroxylic groups by reaction of methoxy aryloxy- or methoxy oligoethyleneoxy-substituted cyclo- and polyphosphazenes with boron tribromide or trimethylsilyl iodide and their use for the preparation of new phosphazene-based materials (e.g., sol-gel hybrids, thermosetting resins, azodyes, cyclolinear inorganic–organic polymers sometimes containing chiral units, or organic macromolecules having cyclophosphazene residues as pendant groups); and the preparation of oxazoline-containing cyclic and polymeric phosphazene derivatives for the synthesis of photoinitiators, chain extenders, or blend compatibilizers. The possible developments of this research are also envisaged.

Syntheses of Chiral Cyclotriphosphazenes and Their Use in Cyclolinear Polymers

The reaction of hexachlorocyclotriphosphazene with two equivalents of the chelating diols 2,2′-dioxybiphenyl and 2′,2′′-dioxy-1′,1′′-bi-2-naphthyl was investigated. Although a mixture of different stereoisomers may be expected, only the formation of the meso-compounds [(R,S)-(O,O)2Cl2P3N3] is found (O,O stands for the diolate). Interestingly, when the remaining PCl2 group undergoes reaction with hard nucleophiles like 4-methoxy phenolate, a change of configuration at one phosphorus center is observed and racemic mixtures of chiral [(R,R)-(O,O)2(RO)2P3N3] and [(S,S)-(O,O)2(RO)2P3N3] phosphazenes are observed. Enantiomerically pure cyclotriphosphazenes were obtaines from either the (R)- or (S)-form of 2′,2′′-dioxy-1′,1′′-bi-2-naphthyl. Soft nucleophiles like amines, however, do not affect the configuration at the phosphorus centers and allow the synthesis of meso-[(R,S)-(O,O)2(R1RN)2P3N3] compounds. the bifunctional cyclotriphosphazenes [(O,O)2(4-OH–C4H4O)2P3N3] and [(R,S)-(O,O)2(H2N)2P3N3] were used in polyaddition reactions with hexymethylene di(isocyanate) to give cyclolinea polymers of different stereochemical compositions corresponding to the stereochemistry of the phosphazene precursor (i.e. either a racemic mixture of homochiral polymer strands, enantiomerically pure polymers, or the meso-form of polymers was obtained). The properties of these polymers are discussed and a mechanism for the change of stereochemistry is proposed.

Plasma surface treatment of poly(acrylonitrile) films by fluorocarbon compounds

Abstract This paper concerns the use of the low-pressure plasma process to confer an hydrophobic character to poly(acrylonitrile) films, without altering their bulk properties. Plasma based fluorination processes using saturated fluorine compounds such as CF 4 , C 6 F 14 and mixtures CF 4 /H 2 were used. Such treated polyacrylonitrile films were characterized by XPS analysis, infrared (ATR) spectroscopy and contact angle measurements. The use of CF 4 led to the fluorination of the film surfaces. Indeed, XPS spectra showed the presence of -CHF-, -CF 2 - and -CF 3 groups. Moreover, the contact angle θ which was 63° for untreated PAN films increased to 115°. Fluorine incorporation in the PAN disappeared when hydrogen is added to CF 4 . In the case of treatment by C 6 F 14 , fluorination was accompanied by a polymerization, as evidenced by XPS with the disappearance of the N 1s photopeak corresponding to the C≡N functions in PAN. By considering the deposition of F- containing layer thickness, it was possible in this latter case to follow the surface modifications by ATR-i.r. spectroscopy.

Hybrid materials based on metal oxides and poly(organophosphazenes)

In this paper the sol-gel preparation of hybrid materials made of metal oxide and polytorganophosphazenel components is described. The main problem focused on during this research was to avoid phase separation in order to get homogeneous materials. This problem was pursued looking at the formation of genuine chemical bonds between the exploited polyphosphazenes and the inorganic composite networks. Investigations on the thermal, mechanical, and electroconductive properties of the synthesized, phosphazene-containing composite materials showed that these matrices presented improved mechanical and thermal features with respect to those of the original phosphazene macromolecule, while the ionic conductivities of the prepared molecular hybrids doped with lithium or silver trillate are of the same order of magnitude as those measured for the neat, original phosphazene substrate.

New heat-resistant polyurethanes prepared from hydroxylated cyclotriphosphazenes

Abstract The reactions of the dihydroxylated cyclotriphosphazenes, (3,5-dihydroxyphenoxy)(pentaphenoxy)cyclotriphosphazene 1 and 2,2-bis(4-hydroxyphenoxy)- bis[spiro(2′,2″-dioxy–1′, 1″-biphenylyl)]cyclotriphosphazene 2 with hexamethylene 1,6-diisocyanate (HDI) lead to the new cyclotriphosphazene containing polyurethanes 3 and 4 , respectively. The condensation polymerization of 1 and 1,3-bis(hydroxy)benzene 5 , or of 2 and 3,3′-(ethylenedioxy)diphenol 6 in a one step reaction allowed us to synthesize the copolymers poly( 1 –co– 5 ), and poly( 2 –co– 6 ). The thermal stability and degradation behavior of 3 , 4 and copolymers were investigated by thermogravimetric analysis in air, and compared with that of polyurethanes synthesized from the 5 -HDI and 6 -HDI reactions. The evolution of the IR spectra and thermogravimetric analysis curves of the copolymers vs the cyclotriphosphazene content were studied.

Surface grafting of a poly(organophosphazene) onto poly(vinyl alcohol) and poly(ethylene-co-vinyl alcohol) using triethoxysilane as a coupling agent

Triethoxysilane HSi(OEt)3 was used as coupling agent to graft a poly(organophosphazene) (POPZ) containing allylic functions to the surface of poly(vinyl alcohol) or poly(ethylene-co-vinyl alcohol) films. Hydrolyzed HSi(OEt)3, which contained both inorganic (Si–OH) and organic (Si–H) reactivities, acted at the interface between the hydroxylated substrates (via a condensation reaction) and the allylic functions in POPZ (via a hydrosilylation reaction). Starting materials and grafting surfaces were studied by ATR-IR and XPS spectroscopies and contact angle measurements. Data obtained indicated that different POPZ layers were produced, depending on whether the functionalization of materials with silane, and the grafting reaction were separately or simultaneously made. The POPZ layer thickness was higher when the grafting reaction was preceded by the POPZ functionalization. In each cases, the modified surfaces showed marked increases in hydrophobicity character.

Conformational stability and force field of chloromonophosphazenes: MNDO calculations, vibrational spectra and normal coordinate analyses of Cl3PNP(X)Cl2 (X = O, S) and [Cl3PNPCl3][Y] (Y = Cl, PCl6)

Abstract The potential energy around the PN bonds for the Cl 3 PNP(X)Cl 2 (X = O, S) molecules and [Cl 3 PNPCl 3 ] + cation have been derived from MNDO (modified neglect of diatomic overlap) calculations. The most stable conformations are two s-trans isomers in nearly eclipsed forms. The calculated structural parameters agree well with the X-ray experimental data. Barriers of 6 and 1.5 kJ/mol for the rotations of the POCl 2 and PCl 3 groups are predicted. In addition, the Raman spectra and the qualitative depolarization measurements for these molecules in the liquid phase have been obtained. All the data indicate that the molecules exist as a mixture of two rotamers in the molten phase. These two conformers are stabilized in the crystal packing of Cl 3 PNP(O)Cl 2 . The observed frequencies are in good agreement with the calculated values obtained by normal coordinate analysis. The MNDO calculation of the harmonic force field is in reasonable agreement with the experimental values. The force-constant values assigned to the torsional modes around the PN bonds correspond to low barriers for the internal rotations. These easy internal rotations around the PN and PN bonds can explain the flexibility of the phosphazene backbone and the elastomeric properties of the polyphosphazene polymers.

Synthesis and structure of new eight-membered Si–O–λ5σ4–P heterocycles

The reaction of Bu2tSi(OLi)21 with PhPOCl2 or of Ph2Si(OLi)2 with POCl3 in a 1:1 molar ratio leads to the formation of the 1,3,3,7-tetraoxa-2,6-disila-4,8-λ5σ4-diphosphacyclooctanes 5 and 9, respectively. An X-ray structure analysis shows 5 to contain an eight-membered Si2O4P2 ring in the chair conformation. The Si–O (1.65 A) and P–O 1.57 A bond lengths in the ring lie within the typical range; the terminal PO oxygen centres are in an axial position and oriented trans with respect to the central Si2O4 plane.

Syntheses of phosphorus containing hydrolytically stable multisite receptors

Abstract Facile condensation reactions between 4′-formylbenzo-15-crown-5 and tris and hexa-hydrazino substituted phosphorus compounds lead quantitatively to three new polymacrocyclic compounds 3a,b and 5 .