WO1992021651A1

WO1992021651A1 - Novel propenyl-functionalized aromatic compounds

Info

Publication number: WO1992021651A1
Application number: PCT/GB1992/000995
Authority: WO
Inventors: Ian Hamerton; John Michael Barton; John Charles Stedman
Original assignee: University of Surrey
Current assignee: University of Surrey
Priority date: 1991-06-04
Filing date: 1992-06-03
Publication date: 1992-12-10
Anticipated expiration: 1993-12-04
Also published as: GB9111940D0

Abstract

Novel bis(3-propenyl-4-cyanatidophenyl) and bis(3,5-dipropenyl-4-cyanatidophenyl) compounds of respective general formula (I), in which A is H- or CH3-CH=CH-, X is -CH2-, -CR2-, -C(=O)-O-, -Y-, or -Z-(-Y-Z-)n, where R has 1-4 carbon atoms and is alkyl or perfluoroalkyl, Y is a direct bond, O, CO, S, or SO2, Z is arylene (preferably para- or meta-phenylene), each Y and Z may be the same or different where occurring more than once, and n is 0 or an integer in the range 1 to about 30 such that the compound has a molecular weight of not more than 10,000 are prepared using as starting material a diallyl or tetra-allylbis-phenol containing the desired group X, which is isomerized to the dipropenyl or tetrapropenylbis-phenol by heating under reflux with potassium hydroxide in methanol. The phenolic groups are esterified to cyanate ester groups using cyanogen bromide and triethylamine, and the compound having both cyanate and propenyl functions is obtained as predominantly the trans geometrical isomer. It may be polymerized alone or preferably by co-reaction with bis-maleimides, bis-citraconimides, aspartimides, compounds containing epoxide groups or other cyanate esters. The polymeric products may serve as matrix resins for structural composites and laminating resins for microelectronic applications, e.g., in the manufacture of printed circuit boards. Carbon-fibre reinforced laminates incorporating compounds of the invention with commercial bis-maleimides and cyanate ester monomers were found to display markedly improved mechanical properties, with particular regard to fracture toughness, and processability compared with the homopolymers.

Description

NOVEL PROPENYL-FUNCTIONALIZED AROMATIC COMPOUNDS

This invention relates to b ..(3-propenyl-4-cyanatidophenyl) and bis(3,5- ipropenyl-4-cyanatidophenyl) compounds of the general formula

in which A is H- or CH₃-CH=CH-, X is -CH₂-, -CR₂-, -C(=0)-0-, -Y-, or -Z-(-Y-Z-)_n, where R has 1-4 carbon atoms and is alkyl or perfluoroalkyl, Y is a direct bond, 0. CO, S, or SO2, Z is arylene (preferably para- or mew-phenylenej, each Y and ^'/. may be the same or different where occurring more than once, and n is 0 or an integer in the range 1 to about 30 such that the compound has a molecular weight of not more i an 10, 000.

These compounds having both cyanate and propenyl functionalization are new. In common with other resin systems based on cyanate esters, they may be polymerized alone or preferably by co-reaction with b/Vmaleimides (BMIs), b/s-citraconimides, aspartimides, compounds containing epoxide groups or other cyanate esters such as d ic yanate ester prepolymers, e . g . , prepolymer of 2,2'-b ^ ( 4 - yanatidophenyl)isopropylidene. The polymeric products may find application in such areas as the aeronautical and automotive industries. They have a suitable combination \^' heat resistance, toughness, low dielectric loss and low moisture absorption, and may serve as matrix resins for structural composites and laminating resins for microelectronic applications, e.g., in the manufacture of printed circuit boards.

JP A 1-306405 published 11 December 1989 described some cyanate- i^'unctionalized esters in which the additional functionalization was allyl rather than propenyl, and one of these monomers has been evaluated in this work as a reference standard.

As well as undergoing cyclotrimerization through the cyanate groups, the allyl- fimctionalized compounds are believed to react with comonomers such as bis- maleimides by a sequence of ENE/Diels-Alder reactions. They are generally less reactive than the propenyl-functionalized compounds of the present invention which probably undergo a Diels-Alder reaction without a preliminary ENE reaction.

Certain propenyl-functionalized phenoxy compounds without cyanate groups have been described by H. D. Stenzenberger, British Polymer Journal 20 (1988) 383- 396 and references cited therein. The compounds obtained were liquid and appeared to be unseparated mixtures of trans and cis geometrical isomers about the C=C double bond.

The compounds of the present invention which have both cyanate and propenyl functions are obtained as predominantly the trans geometrical isomer (the transxis ratio may vary from 20:1 to 4:1) which may be isolated as a crystalline solid.

The compounds of the present invention are conveniently prepared using as starting material a 3.3'-diallyI or 3,3',5,5'-tetra-allylbi5-phenol containing the desired group X, which itself may be made by hearing the bis -phenol by heating with allyl bromide in the presence of sodium hydroxide to give the di-allyl to-phenol and then treating the latter in the same way to give the tetra-allyl bis-phenol. The allyl tø-phenol is then isomerized to the propenyl bw-phenol by heating under reflux with potassium hydroxide in methanol as described in GB 2012781 A published 1st October 1979, and the phenolic groups are esterified to cyanate ester groups using cyanogen bromide and triethylamine. Although the final products are novel, the chemistry involved in the preparative steps is well known.

Formulation of Functionalized Cyanate Ester Copolymers

For the formation of e.g., a functionalized cyanate ester/b/.,-maleimide copolymer, the comonomers (and catalytic blend if desired, e.g., a transition metal helate or carboxylate such as copper(II) naphthenate, 300 ppm Cu²⁺ and an involatile phenol such as nonylphenol, 4 parts per hundred parts resin) are heated gently with stirring until both become molten. The reactants are then quenched to form a prepolymer blend which on further heating may react to form the desired copolymer. By varying the extent to which the comonomers are heated, and hence the degree of reaction, the rheological properties may be tailored to the specific application.

The following examples illustrate the invention, with the intermediate and final products obtained from the di-allyl derivatives of 2,2^'-b .. - ( 4 - hydroxyphenyljisopropylidene ("bis-phenol-A"), 2,2'-bw-(4-hydroxyphenyl) hexafluoroisopropylidene ("bis-phenol-AFβ") and b/._-(4-hydroxyphenyl)sulphone ( "b 5-phenol-S"). All reagents and solvents were reagent-grade quality, purchased commercially (except the di-allylb ^-phenol-A which was supplied by Ciba-Geigy UK) and used without further purification unless otherwise noted.

*H n.m.r. spectra were recorded at 298K in Dg-acetone using a Bruker AC300 pulse Fourier transform nuclear magnetic resonance spectrometer operating at 300 MHz. The chemical shifts (6) are given in parts per million (ppm) and are reported relative to the tetramethylsilane (TMS) internal standard.

Infra-red spectra were recorded with a Perkin-Elmer 1750 Fourier transform infra-red spectrometer interfaced with a Perkin-Elmer 7300 computer; the samples were presented as either thin films or as KBr disks depending on the physical state of the material.

Both the FT-IR and ^lH n.m.r. techniques were readily applicable in determining that the cyanation step had been successful and in determining the isomeric composition of the resulting product.

Dynamic differential scanning calorimetry (DSC) was performed at 10K min^-1 using a Du Pont 910 calorimeter interfaced with a Du Pont 9900 computer/thermal analyzer. Accurately-weighed monomer samples of 3±1 mg were analyzed in sealed, tincoated aluminium pans under nitrogen (40 ml min"¹).

Dynamic mechanical thermal analysis (DMTA) was carried out on cured neat resin samples using a Polymer Laboratories dynamic mechanical thermal analyzer interfaced with a Compaq Diskpro 286 personal computer (running P.L. software). The resin samples were oscillated in a single cantilever flexural mode at a fixed frequency of 10 \ Iz while being scanned under nitrogen over a temperature range of 50 to 500°C at a heating rate of 2K min^{- 1}. The glass transition temperature, T_g, is taken as the peak maximum in the loss modulus, E".

The melting points were determined using a Koffler hot-stage microscope.

Other products according to the invention may be obtained similarly using the di-allyl or tetra-allyl derivatives prepared from other bzs-phenols, such as bis(4- hydroxyphenyl) sulphide, b i^,(4-hydroxyphenyl) ether, b j'(4-hydroxyphenyl) ketone and 4.4'-dihydroxy-biphenyl, by heating with allyl bromide in the presence of sodium hydroxide.

Example 1. 2,2'- Bis(3-propenyl-4-cyanatidophenyI) isopropylidene (1)

A one-litre, three-neck flask, fitted with a still-head and condenser for a downward distillation, was charged with 2,2' -bis { - a l l y l - 4- hydroxyphenyI)isopropylidene (50 g, 162 mmol) and a saturated solution (ca. 50 % w/v) of potassium hydroxide in methanol (150 ml). The mixture was distilled slowly (collecting methanol in the receiving flask) until the temperature of the bulk liquid reached 110°C. The still- head was removed, an air condenser put in its place, and the reaction mixture boiled gently under reflux for six hours. The reaction mixture was cooled to room temperature, acidified with concentrated hydrochloric acid (20 ml.) and xtracted into dichloromethane (3 x 30 ml). The crude product was concentrated on me rotary evaporator to yield a very viscous amber oil with a pungent odour. ¹F n.m.r. analysis revealed that the crude product contained a mixture of geometric isomers (both trans and cis about the propenyl C=C double bond) in the approximate ratio 4:1 {trans.'cis).

At this stage of the preparation the crude intermediate was used directly without lurther purification (nor isolation of discrete isomers) in the ensuing cyanation reaction.

*H n.m.r. analysis revealed that the conversion from the allyl- to the propenyl- substituted b/s-phenol was almost quantitative. The allyl and propenyl groups both gave rise to splitting patterns that were markedly different, and no chemical shifts corresponding to the allyl protons were visible on the 300 MHz *H n.m.r. spectrum of tiie sample isomerized to the propenyl derivative.

¹ H-nmr spectral assignments for 2,2'-b j^,(3-propenyl-4-hydroxyphenyl)isopropylidene (300 MHz, D₆-acetone, ppm from TMS)

A three-neck, half-litre round-bottom flask equipped with a dropping funnel, overhead stirrer. and thermometer was charged with the newly prepared 2,2'-bis(3- propeπyl-4-hydroxyphenyl)isopropylidene (47.3 g, 153.2 mmol), cyanogen bromide (45.09 g, 0.43 mol) and freshly distilled acetone (200 ml). The flask was cooled to -30°C and freshly distilled triethylamine (43.08 g, 0.43 mol) was added dropwise over 45 minutes to the vigorously stirred mixture while the temperature was maintained at -25 to -30°C by immersion in a Dewar flask containing a mixture of acetone and liquid nitrogen. The reaction mixture was stirred for a further 90 minutes while warming to room temperature, and the product isolated by slowly decanting the solvent from the reaction mixture into ice water (1.5 litres) whilst adding ice water (1 litre) to the remaining precipitated salts. After repeated extraction into dichloromethane (9 x 50 ml) and concentration on a rotary evaporator, the crude product was a mobile amber liquid. Purification by means of column chromatography (Brockman BDH grade 1 activated silica, with a dichloromethane eluent) produced a straw coloured, pungent oil in good yield (ca. 40 g).

Upon standing for approximately a week at room temperature, large waxy, white crystals formed in the bottom of the flask containing the crude oil, and a portion of this crystalline product was dried (removing the surplus oil coating it), m.p. 72- 7 °C. Rapid cooling by refrigeration quickly produced a crop of the product as a microcrystalline powder which was easily separated from the oil by filtration. *H n.m.r. and X-ray diffraction analysis of a single crystal revealed that it consisted of the i runs isomer. Η-nmr spectral assignments for

cyanatidophenyl)isopropyIidene (300 MHz, D6-acetone, ppm from TMS) δ Multiplicity Assignment 7.56-7.54 doublet 2 x Ar-H 7.47-7.44 doublet of doublets 4 x Ar-H 7.34-7.25 doublet of doublets 4 x Ar-H 6.59-6.53 complex multiplet 2 x CH=CH-Ar 6.43-6.29 complex multiplet 2 x CH=CH-CH₃ 1.96-1.87 doublet of doublets 2 x CH=CH-CH₃ 1.75 singlet 2 x isopropyl CH

FT-IR spectrum of 2,2'-b^(3-rrα/is--propenyl-4-cyanatidophenyl)isopropylidene

(KBr disk) cm"¹ 3063 weak 1640 weak 1172 very strong

2977 strong 1611 weak 1135 very strong

2936 moderate 1594 weak 935 moderate

2S77 weak 1493 very strong 820 moderate

2272 strong 1453 moderate 780 moderate

2 1 1 strong 1203 strong

The product thus appeared to exist as two geometric isomers in distinctly different physical states. The rrα/tf-isomer crystallized as a waxy white solid, while the t zv-isomer remained as a mobile amber oil at room temperature.

The FT-IR spectrum of the product displayed the appearance of an intense doublet at 2272 cm"¹ and 221 1 cm^{- 1} corresponding to the C≡N stretch and enaracteristic of compounds bearing the cyanato group. This was accompanied by the disappearance of the intense broad absorbance at ca. 3300-3600 cm"¹ corresponding to the O-H stretch of tø-phenols and was of greatest diagnostic use in this respect.

Example 2. 2,2'-Bis(3-propenyl-4-cyanatidophenyl) hexafluoroisopropylidene (2)

The product was prepared substantially as described in example 1. The diallyl ether was first prepared from 5 g (12 mmole) of 2,2'-bj._(4-hydroxyphenyl) hexafluoroisopropylidene (b/s-phenol-AFό) by treatment with sodium hydroxide and two molar equivalents of allylbromide in a toluene/water mixture containing a tetramethylammonium bromide - a phase transfer catalyst (and heating the resulting mixture at 50-60°C for twenty hours). The diallyl-b/_^*-phenol was then prepared from the diallyl ether via a Claisen rearrangement by heating at ca. 200-205°C for twenty- four hours. 4.55 g (0.01 mole, 86% yield) of the desired product 2,2'-b/.s(3-propenyl- 4-cyanatidophenyl)hexafluoroisopropylidene was obtained as a cream coloured solid (mp 83°C). H-n.m.r. analysis revealed that the isomers were isolated in a transxis ratio of 4: 1.

ϊH-n.m.r. spectral assignments for 2,2'-b/.,(3-propenyl-4- cyanatidophenyl)hexafluoroisopropylidene (300 MHz, D6-acetone, ppm from TMS)

FT-IR spectrum of 2,2'-b j(3-propenyl-4- cyanatidophenyl)hexafluoroisopropylidene (Nujol mull) cm^*1 3063 weak 1650 weak ^• 1170 very strong

2977 strong 1610 moderate 1135 very strong

2936 strong 1500 moderate 980 moderate

2877 moderate 1460 strong 820 moderate

2830 moderate 1250 very strong 760 moderate

2215 moderate 1203 very strong

Example 3. Bϊs(3-propenyl-4-cyanatidophenyl)sulphone (3)

The product was prepared substantially as described in example 1. The diallyl ether was first prepared from 5 g (15 mmole) of to(4-hydroxyphenyl)sulphone (bis- phenol-S) by treatment with sodium hydroxide and two molar equivalents of allylbromide in a toluene/water mixture containing a tetramethylammonium bromide - a phase transfer catalyst (and heating the resulting mixture at 50-60°C for fifteen hours). The diallyl-bw-phenol was then prepared from the diallyl ether via a Claisen rearrangement by heating at ca. 200-205°C for twenty-four hours. 4.90 g (13.8 mmole, 92% yield) of the desired product b _^*(3-propenyl-4-cyanatidophenyl) sulphone was obtained as an amber solid (mp 106°C). ^-n.m.r. analysis revealed that the isomers were isolated in a transxis ratio of 20:1. 'H-n.m.r. spectral assignments of bι^*5(3-rrα« -propenyl-4-cyanatidophenyl)sulphone (300 MHz, Dό-acetone, ppm from TMS) δ Multiplicity Assignment 8.26 doublet 2 x Ar-H 8.10-8.06 doublet of doublets 2 x Ar-H 7.81-7.72 doublet of doublets 2 x Ar-H 6.56-6.51 doublet 2 x trans-CR-CH-Ar 6.47-6.40 doublet of doublets 2 x c«-CH=CH-Ar 6.32-6.23 complex multiplet 2 x rrα^-CH=CH-CH₃ 5.85-5.70 complex multiplet 2 x cώ-CH=CH-CH₃ 1.76-1.73 doublet of doublets 2 x trans-CH=CH-CU 1.67-1.64 doublet of doublets 2 x ct_--CH=CH-CH₃

FT-IR spectrum of bw(3-rranj-propenyI-4-cyanatidophenyl)sulphone (Nujol mull) cm^-1 3063 weak 1280 strong 1080 strong

22(X) moderate 1230 strong 970 moderate

1 50 moderate 1180 strong 900 moderate

1 80 moderate 1160 strong 830 moderate

1 (X) moderate 1120 strong 720 moderate

1 00 stron « 1100 stron ε 700 strong

Dynamic DSC data for Cyanate ester monomers, blends and comonomers

The analyses were carried out on uncatalvzed monomer and copolymer blends and hence represent the thermal polymerization behaviour. The following designations are used:

2,2'-bw(3-propenyI-4-cyanatidophenyl)isopropylidene

(2) 2,2'-bw(3-propenyl-4-cyanatidophenyl)hexafluoroisopropylidene <3) bz_^*(3-propenyI-4-cyanatidophenyI)sulphone

(4» 2.2'-b/,_(3-allyl-4-cyanatidophenyl)isopropyIidene

(5j Commercial 'AroCy B-30' dicyanate ester prepolymer (30% converted homopolymer) of 2.2'-ό«(4-cyanatidophenyl)isopropylidene (produced by

Rhone-Poulenc). (6) Commercial near-eutecticbw-maleimide blend 'Compimide 353' (produced by Shell Technochemie and containing three BMI co-monomers).

( 7 ) b/_-(4-maleimidophenyl)methane

The allyl-functionalized cyanate ester (4) was used as a standard against which the properties of the new materials might be gauged. In the first instance, the relative reactivity of the functionalized cyanate esters was assessed using dynamic DSC (Table 1 ). The allyl derivative (4) displays a higher polymerization onset temperature than the propenyl analogue (1) by some 40°C indicating the greater thermal reactivity of the latter.

Table 1. Thermal characteristics of functionalized cyanate ester monomer and copolymers.

Sample T_m (°C) T₀nset (°C) T_max (°C) ΔH (J/g)

T_m Crystalline melt endotherm

Tonsci Onset of polymerization

Tmax Exothermic peak maximum (or maxima).

Analysis of Composite Properties

In their proposed application as polymeric matrices for structural composites it is important that the new materials display not only acceptable strength, but also greatly improved fracture toughness over existing thermosetting resins (which is generally a shortcoming of such materials). A range of BMI Cyanate ester homopolymers, blends and copolymers were fabricated into unidirectional carbon fibre-reinforced laminates.

For the preparation of carbon fibre-reinforced laminate samples, the prepolymer blend (containing the cyanate esters and b s-maleimides) was applied to Courtaulds XAS carbon fibre (containing 1% epoxy size) by solution coating in a volatile transport solvent (dichloromethane or acetone) and then wound onto a drum to form prepreg. The unidirectional laminates were laid up (10- or 18-ply, 0°) and, after drying in an oven at 50°C for one hour to remove residual solvent, underwent the following curing cycle in an autoclave. After lay-up on the bed plate a vacuum was applied (and held overnight). A pressure of 6 bar (100 psi) was applied at the start of the run and the vacuum vented when the pressure reached 2 bar. The temperature was raised at 2°C min^*-1 to 180°C and then held at 180°C for 3 hours. The cured panels were then cooled at 3°C min^-1 to 65°C before being released from the bed plate.

Measurements of flexural strength (fp) and modulus (Ef), 0° compression strength < FLC)_' interlaminar shear strength (ILSS) and fracture toughness (Gic) were carried out using techniques outlined in R.A.E. Technical Report 88012 "CRAG Test Methods for the Measurement of the Engineering Properties of Fibre-reinforced PLastics", P.T. Curtis (Ed published in 1988. The results quoted are a mean of at least five samples ' four amples in the case of Gic analysis). Specific gravity and fibre content analysis were carried out by the Analytical and General Chemical Section of the Defence Research Agency (Aerospace Division) Famborough using standard methods.

In order to assess the effect of incorporating the new material into a BMI resin, a coarse formulation containing 33% of the sample (1) was prepared. Even in this initial case, the mechanical results demonstrated that in many of the formulations an improvement in the measured parameters {e.g., ILSS and fj?) over those of the homopαlymers was observed (Table 2). In particular a very marked enhancement in fracture toughness over the BMI and cyanate homopolymers was obtained.

Table 2. Mechanical Data from Unidirectional CF-Laminates^(a)

Sam ple Molar SG<^bV% Fibre I LSS fF Ef ^L C Gιc^(a)

Ratio (MPa) (GPa) (GPa) (GPa) (JπT²)

10- P ly 18-P Iy

6 - 1.60/ 1.56/ 106.8 1.22 73.7 1.50 162

62.1 65.4

5 - 1.54/ 1.61/ 79.7 0.98 68.2 1.11 231

63.7 74.4

5+6 1/1 - 1.58/ 94.5 1.97 81.9 1.10 394

73.1

4+6 1/1 1.58/ 1.55/ 88.1 1.20 73.6 1.56 430

71.8 73.5

4+5+6 1/1/1 1.55/ 1.56/ 77.8 1.16 67.8 1.33 300

67.0 72.6

1 +6 1/1 1.50/ 1.61/ 108.0 1.57 53.0 0.98 330

59.1 82.7

1 +5+6 1/1/1 1.54/ 1.60/ 95.8 1.55 63.1 1.24 438

63.2 73.2

^('" Fracture Toughness tests carried out on 18 ply Unidirectional Carbon Fibre- reinforced Laminates (Gic Corrected Beam Theory quoted at maximum load). ^lll) Specific gravity of laminate.

The coarse formulations (Table 2) relates to mixtures containing 50% and 337c of the new material ( 1). It is envisaged that the new propenyl-functionalized cyanate esters will be used in smaller quantities in a BMI blend as toughening modifiers and so a range of formulations was prepared in which the BMI content (6) was fixed at 50% and the ratio of cyanate esters (5 and 1) was varied (Table 3). In this way it was hoped that an optimum ratio of functionalized:commercial cyanate ester might be determined.

Table 3. Mechanical Data from Unidirectional CF-Laminates^(a) (BMI ratio fixed at 50%)

Monomer Ratio SG/% Fibre ILSS/ f_F/ E_f/ F_LC/ G_Ϊ I

MPa GPa GPa GPa Jπr² (6): (5): (1 ) 10-PIy 18-Ply

50:40:10 1.55/ 1.58/ 99.7 1.78 69.2 1.15 294

66.0 71.7

50:30:20 1.57/ 1.56/ 104.4 1.34 39.7 0.87 197

70.7 69.2

50:20:30 1.58/ 1.61/ 104.5 1.55 47.2 0.94 233

72.1 72.7

50:10:40 1.51/ 1.53/ 106.0 1.63 53.9 1.08 226

62.3 66.0

^u Fracture Toughness tests carried out on 18 ply Unidirectional Carbon Fibre- reinforced Laminates (Gic Corrected Beam Theory quoted at maximum load).

The data in Table 3 clearly demonstrate that a formulation containing just 10% of the propenyl-functionalized ester (1) produces optimal properties in nearly all of the mechanical properties studied. Hence, the cyanate composition ratio of (4:1) (between monomers (5):(l)j was kept constant and the BMI content in the blend was varied in order to further extend this crude formulation.

Table 4. Physical Data from Unidirectional CF-Laminates^,a^ (fixed ratio of cyanate ester monomers (5) and (1) of 4:1)

Monomer Ratio ILSS/ f_F/ E_f/ F_{L C}/ G__c/

MPa GPa GPa GPa Jm-² (6):Cvanate^(b)

Laminate cannot be fabricated without excessive void content leading to inconsistent results.

⁽a⁾ Fracture Toughness tests carried out on 18 ply Unidirectional Carbon Fibre- reinforced Laminates (Gic Corrected Beam Theory quoted at maximum load). ft>⁾ Total combined cyanate ester content (in a fixed 4: 1 ratio of (5):(1)).

The data in Table 4 clearly show that in this crude formulation study an optimum value for the fracture toughness (Gic) of 383 Jπr² is obtained when the BMI resin blend is modified with 40% cyanate ester (i.e., 10% of the novel propenyl-functionalized cyanate ester (1)). This produces a marked enhancement in the cured resin over the fracture toughness of unmodified BMI and cyanate ester homopolymers of 162 and 23 Urn^-2 respectively.

DMTA analyses of several representative laminate samples (each having first undergone a free-standing postcure of 6 hours at 220°C) were also undertaken. The results are presented below in Table 5. It should be noted that the unmodified 'Compimide 353' blend (6) displayed a T_g in the region of 323°C, while a blend of monomers (5) and (6) produced two apparent T_g values at 219°C and 300°C (consistent with the Tg values of each of the homopolymers - indicating the formation of an interpenetrating network polymer ). Finally a blend of monomers (6)+(5)+(l) in the ratio (50:40:10), i.e., a blend containing 10% (by molar equivalence) of the novel modifier (1 ), produced a network with a single T_g at 300-316°C - indicating the formation of a terpolymeric network.

Table 5. Dynamic Mechanical Data from Unidirectional CF-Laminates

Sample

(6)

(6)+(5)

(6)+(5)+(l)

It is also worthy of note that in common with data produced from the homopolymer (5), an increase in the amount of (5) in the composition leads to the production of laminate samples with an unacceptable void content (this is thought to be due to the volatility of the dicyanate ester monomer). It is thought that by introducing the propenyl functionality (which is able to co-react with, e.g., BMIs) the more rapid formation of a terpolvmer network formation is encouraged - thus incorporating the volatile commercial dicvanate and resulting in an acceptable laminate sample.

Claims

1. A propenyl-functionalized aromatic compound of the general formula

in which A is H- or CH₃-CH=CH-, X is -CH₂-, -CR -, -C(=0)-0-, -Y-, or -Z-(-Y-Z-)_n, where R has 1-4 carbon atoms and is alkyl or perfluoroalkyl, Y is a direct bond, O, CO, S, or SO2, Z is arylene (preferably para- or erα-phenylene), each Y and Z may be the same or different where occurring more than once, and n is 0 or an integer in the range 1 to about 30 such that the compound has a molecular weight of not more than 10, 000.

2. β/._(3-propenyl-4-cyanatidophenyl) isopropylidene

3. β/._(3-propenyl-4-cyanatidophenyl) hexafluoroisopropylidene

4. β/..(3-propenyl-4-cyanatidophenyι) sulphide

5. βw(3-propenyl-4-cyanatidophenyl) sulphone

6. 3,3'-Dipropenyl-4,4'-dicyanatido-biphenyl

7. β .v-4-(4-cyanatido-3-propenylphenyleneisopropylidene-4-phenoxy-4- phenylene) sulphone

8. β/ (3,5-dipropenyl-4-cyanatidophenyl) isopropylidene

9. A compound as claimed in any one of claims 1 to 8 in which the propenyl groups are essentially all in the trans configuration.

10. A method of making polymeric resins which comprises polymerizing a compound as claimed in any one of claims 1 to 9 alone or preferably by co-reaction with a b/rS-maleimide, a b/s-citraconimide, an aspartimide, a compound containing epoxide groups, or a compound containing other cyanate ester groups.

1 1. A method according to claim 10 in which the polymerized resins form the matrix of a structural composite.

12. A method according to claim 1 1 in which the resins are fabricated into laminates reinforced with carbon fibre.

13. A method according to claim 12 in which the resins comprise a compound as claimed in any one of claims 1 to 9 and a dicvanate ester prepolymer of 2,2'-bis(4- cyanatidophenyl)isopropylidene in the monomer molar ratio of approximately 1 :4 polymerized together with b/s-maleimide.

14. A method according to claim 13 in which the b/s-maleimide to total cyanate ester ratio is approximately 3:2.

15. A polymerized product made by a method claimed in any one of claims 10 to 14.

16. Novel propenyl-functionalized aromatic compounds and polymerized products threreof substantially as herein described with reference to the examples.