PBX composition
11746069 · 2023-09-05
Assignee
Inventors
- Rebecca Elizabeth Stephens (Usk Monmouthshire, GB)
- Richard Stephen Arthur (Porthsmouth, GB)
- Wayne Cord Hayes (Reading, GB)
- Michael Edward Budd (Reading, GB)
Cpc classification
International classification
Abstract
The invention relates to a cast explosive composition. There is provided a precure castable explosive composition comprising an explosive material, a polymerisable binder, said cross linking reagent comprising at least two reactive groups each of which is protected by a labile blocking group. ##STR00001##
Claims
1. A batch process for filling a munition with a cross linked polymer bonded explosive composition, the batch process comprising: forming an admixture of precure castable explosive composition, comprising an explosive material, a polymerisable binder, and a cross-linking reagent comprising a first reactive group protected by a first labile blocking group and a second reactive group protected by a second labile blocking group; filling the munition with the admixture; and causing the removal of the first and second labile blocking groups in situ to furnish said cross linking reagent to the reactive groups.
2. The batch process according to claim 1, further comprising causing the cure of said polymerisable binder to form a polymer bonded cast explosive composition.
3. The batch process according to claim 1, wherein forming the admixture includes selecting the cross-linking reagent comprising a polyisocyanate.
4. The batch process according to claim 3, wherein forming the admixture includes selecting the cross-linking reagent comprising a diisocyanate.
5. The batch process according to claim 3, wherein the first and second labile blocking groups are independently selected from (i) NHR.sup.2R.sup.3, wherein R.sup.2 and R.sup.3 are an alkyl, an alkenyl, a branched-chain alkyl, C(O)R.sup.12, an aryl, a phenyl, or together form a heterocycle, wherein R.sup.12 is an alkyl, an alkenyl, a branched chain alkyl, a branched chain aryl, a phenyl, or R.sup.2 and R.sup.3 together form a lactam; (ii) OR.sup.15, wherein R.sup.15 is an aryl, a phenyl, or a benzyl having at least two nitro groups on the ring; or (iii) O—N═CR.sup.9R.sup.10, wherein R.sup.9 and R.sup.10 are independently selected from an alkyl, an alkenyl, a branched chain alkyl, an aryl, or a phenyl, and wherein at least one of R.sup.9 or R.sup.10 is a branched chain alkyl, a branched chain aryl, or a phenyl.
6. The batch process according to claim 5, wherein the first labile blocking group is the same as the second labile blocking group.
7. The batch process according to claim 1, wherein causing the removal of the first and second labile blocking groups includes heating the admixture.
8. The batch process according to claim 7, wherein heating the admixture is performed to a temperature not greater than 200° C.
9. The batch process according to claim 8, wherein the temperature is in the range of from 50° C. to 150° C.
10. The batch process according to claim 8, wherein the temperature is in the range of from 80° C. to 120° C.
11. The batch process according to claim 1, wherein forming the admixture includes selecting the polymerisable binder comprising a cellulosic material.
12. The batch process according to claim 1, wherein forming the admixture includes selecting the explosive material from RDX, HMX, FOX-7, TATND, HNS, TATB, NTO, HNIW, GUDN, picrite, aromatic nitramine, ethylene dinitramine, nitroglycerine, butane triol trinitrate, pentaerythritol tetranitrate, DNAN trinitrotoluene, inorganic oxidiser, ADN, ammonium perchlorate, energetic alkali metal salt, energetic alkaline earth metal salt, and combinations thereof.
13. The batch process according to claim 1, wherein at least one of the first and second labile blocking groups comprises a sterically hindered branched chain hydrocarbyl group.
14. The batch process according to claim 1, wherein causing the removal of the first and second labile blocking groups results in a polymer bonded explosive composition and one or more protonated blocking groups.
15. A batch process for filling a munition with a cross linked polymer bonded explosive composition, the batch process comprising: forming an admixture of precure castable explosive composition, comprising an explosive material, a polymerisable binder, and a cross-linking reagent comprising a first reactive group protected by a first labile blocking group and a second reactive group protected by a second labile blocking group; partially reacting the polymerisable binder with the cross-linking reagent to result in the admixture including partially polymerized binder-cross-linking reagent, wherein at least one of the first and second reactive groups of the cross linking reagent is protected by the respective first or second labile blocking group; filling the munition with the admixture; and causing the removal of the unreacted first and second labile blocking groups in situ to furnish said cross linking reagent to the first and second reactive groups.
16. The batch process according to claim 15, wherein the first and second labile blocking groups are independently selected from (i) NHR.sup.2R.sup.3, wherein R.sup.2 and R.sup.3 are an alkyl, an alkenyl, a branched-chain alkyl, C(O)R.sup.12, an aryl, a phenyl, or together form a heterocycle, wherein R.sup.12 is an alkyl, an alkenyl, a branched chain alkyl, a branched chain aryl, a phenyl, or R.sup.2 and R.sup.3 together form a lactam; (ii) OR.sup.15, wherein R.sup.15 is an aryl, a phenyl, or a benzyl having at least two nitro groups on the ring; or (iii) O—N═CR.sup.9R.sup.10, wherein R.sup.9 and R.sup.10 are independently selected from an alkyl, an alkenyl, a branched chain alkyl, an aryl, or a phenyl, and wherein at least one of R.sup.9 or R.sup.10 is a branched chain alkyl, a branched chain aryl, or a phenyl.
17. A batch process for filling a munition with a cross linked polymer bonded explosive composition, the batch process comprising: forming an admixture of precure castable explosive composition, comprising an explosive material, a polymerisable binder, and a polyisocyanate having at least a first reactive group protected by a first labile blocking group B and a second reactive group protected by a second labile blocking group B; filling the munition with the admixture; and causing the removal of the first and second labile blocking groups B in situ to furnish said polyisocyanate to the first and second reactive groups.
18. The batch process according to claim 17, wherein the first and second labile blocking groups B are independently selected from (i) NHR.sup.2R.sup.3, wherein R.sup.2 and R.sup.3 are an alkyl, an alkenyl, a branched-chain alkyl, C(O)R.sup.12, an aryl, a phenyl, or together form a heterocycle, wherein R.sup.12 is an alkyl, an alkenyl, a branched chain alkyl, a branched chain aryl, a phenyl, or R.sup.2 and R.sup.3 together form a lactam; (ii) OR.sup.15, wherein R.sup.15 is an aryl, a phenyl, or a benzyl having at least two nitro groups on the ring; or (iii) O—N═CR.sup.9R.sup.10, wherein R.sup.9 and R.sup.10 are independently selected from an alkyl, an alkenyl, a branched chain alkyl, an aryl, or a phenyl, and wherein at least one of R.sup.9 or R.sup.10 is a branched chain alkyl, a branched chain aryl, or a phenyl.
19. The batch process according to claim 18, wherein forming the admixture includes selecting the explosive material from RDX, HMX, FOX-7, TATND, HNS, TATB, NTO, HNIW, GUDN, picrite, an aromatic nitramine, ethylene dinitramine, nitroglycerine, butane triol trinitrate, pentaerythritol tetranitrate, DNAN trinitrotoluene, an inorganic oxidiser, ADN, ammonium perchlorate, an energetic alkali metal salt, an energetic alkaline earth metal salt, and combinations thereof.
20. The batch process according to claim 18, wherein causing the removal of the unreacted first and second labile blocking groups includes heating the admixture in situ to a temperature in the range of from 50° C. to 150° C.
Description
EXAMPLES
(1) General Synthesis of Blocked IPDI
(2) Blocking group B and isophorone diisocyanate were dissolved in THF or CHCl.sub.3 and refluxed until reaction has reached completion. The solvent was removed in vacuo to leave the blocked IPDI as a white solid. The yields are given in Table 1 below.
(3) TABLE-US-00002 TABLE 1 blocked di-isocyanates Ratio of blocking Blocking group group to Yield Compound B IPDI (%)
General Deblocking Method for Compounds in Table 1.
(4) Blocked IPDI (8.68 wt %) was evenly dispersed in a composition of hydroxyl-terminated polybutadiene (91.1 wt %) and dibutyltin dilaurate (0.22 wt %) at 60° C. over a period of 2 hours. The mixture was poured into a cast and cured between 90-120° C. over a period of several days to achieve a cross linked rubber. It was found for all examples there was no reaction between the blocked isocyanate and HTPB in the presence of the catalyst, at 55° C., even when left overnight.
(5) This indicates that the blocking group was not removed until temperatures above 90° C. were employed. Therefore general processing of the precure castable explosive composition may proceed to be mixed, even with slight heating to aid mixing, and that the deblocking only occurs when significant heat is employed to specifically activate and deblock the diisocyanate, such that the cross linking reaction may only proceed once the temperature is raised, to the deblocking temperature.
(6) Dissociation of Blocked-IPDI
(7) The dissociation temperature of the generated blocked isocyanates was undertaken to ascertain the conditions required in order to achieve the cure of the polymer such as, for example HTPB. Techniques such as variable temperature infra-red spectroscopy (VTIR) can be employed to observe the dissociation of thermally-labile oxime-urethanes.
(8) The blocked isocyanates 5.1 to 5.6 were dissolved in dried tetraethylene glycol dimethyl ether in a ratio of 1:0.25 wt. %. This solution was injected into a variable temperature cell and an IR spectrum recorded at 10° C. increments. The dissociation temperature was recorded as the onset at which an absorption characteristic of the isocyanate stretching vibration ˜2250 cm-1 was observed Table 2.
(9) TABLE-US-00003 TABLE 2 Dissociation temperatures of blocked-isocyanates 5.1 to 5.6 measured using VTIR spectroscopy Dissociation Blocking group Temperature (° C.) 5.1 diisopropylamine 100 5.2 □-caprolactam 130 5.4 3,3-dimethyl-2-butanone oxime 120 5.5 imidazole 70 5.6 2,6-dimethylphenol 150
(10) A preferred dissociation temperature may be in the range of 70 to 100° C. Imidazole-blocked IPDI 5.5 began to dissociate at 70° C., well within the desired temperature range. Diisopropylamine-blocked IPDI 5.1 exhibited dissociation at 100° C. and it is expected that increasing the steric hindrance around the bond will lead to a reduction in the dissociation temperature and can be easily achieved by blocking with more sterically hindered amines. 3,3-Dimethyl-2-butanone oxime-blocked IPDI 5.4 began to dissociate at 120° C., although this is above the desired temperature.
(11) The dissociation temperature of oxime-urethanes may also be reduced by increasing the steric hindrance around the oxime.
(12) TABLE-US-00004 TABLE 3 Dissociation temperatures of IPDI blocked with a range of oximes possessing varying degrees of steric hindrance. Dissociation Temperature Blocking Group (° C.) 5.12
(13) The dissociation temperature of the oxime-urethanes 5.12 to 5.16 was measured using VTIR spectroscopy and the results are listed in Table 3, above.
(14) The least sterically encumbered oxime-urethane 5.12 dissociated at 135° C. It was expected the dissociation of 5.13 would occur at the next highest temperature followed by 5.4. However, the dissociation of 5.13 was observed 20° C. below that of 5.4. This result suggests that sterically encumbered Z-oximes have a greater effect on the dissociation temperature than the corresponding E-isomer. Furthermore, the dissociation of 5.14 was observed at the same temperature as 5.13. This steric effect was also observed in aromatic oximes, benzophenone-based oxime-urethane 5.16 dissociating at a lower temperature than the acetophenone analogue 5.15.
(15) Cure of HTPB Using Blocked-IPDI
(16) The potential of these blocked-isocyanates to cure hydroxy-functionalised polymers at elevated temperatures was investigated. The blocked isocyanates 5.1-6 (8.01 mmol) were dispersed in a mixture of HTPB (18.22 g) and DBTDL (0.044 g) using an overhead stirrer at 70° C. In order to achieve uniform curing of HTPB, complete dispersion of the blocked isocyanates within HTPB was desired and indeed 5.1 5.2 and 5.4 exhibited excellent solubility at 70° C. In contrast, imidazole-blocked IPDI 5.5 and 2,6-dimethylphenol-blocked IPDI 5.6 exhibited poor solubility in HTPB and thus efficient dispersion was not achieved.
(17) The mixtures were heated for a period of 72 hours at 120° C. in an evacuated atmosphere. Curing of HTPB was achieved using diisopropylamine-blocked IPDI 5.1—however, as a result of the evolution of volatile diisopropylamine, bubbles were formed within the polyurethane rubber. The high dissociation temperature of caprolactam-blocked IPDI 5.2 (130° C.) prevented the cure of HTPB. The cure of HTPB was successfully achieved using oxime-urethane 5.4. The poor solubility of 5.5 in HTPB prevented the formation of a homogeneously crosslinked polyurethane, thus the formation of a uniformly crosslinked matrix was not achieved. The high temperatures required for the dissociation of 2,6-dimethylphenol-blocked IPDI 5.6 and its poor solubility in HTPB prevented the formation of a polyurethane matrix (Table 4).
(18) TABLE-US-00005 TABLE 4 Solubility and curing capability of blocked isocyanates 5.1-6 in HTPB Soluble in Cure of Blocking group HTPB(70° C.) HTPB (120° C.) 5.1 diisopropylamine yes yes 5.2 caprolactam yes no 5.4 3,3-dimethyl-2-butanone oxime yes yes 5.5 imidazole no no 5.6 2,6-dimethylphenol no no
(19) These results identify that oxime-urethanes possess the ideal properties required for their potential employment in explosive formulations—soluble in HTPB, low volatility of released oxime and relatively low dissociation temperature that could be decreased by modification of the steric and electronic properties of the oxime.
(20) Electron Effects on the Dissociation of Oxime-Urethanes
(21) A range of oxime-urethanes using acetophenone oxime analogues were generated that contain electron-withdrawing and electron donating moieties at the ortho, meta, and para-positions. The dissociation temperatures of the generated oxime-urethanes were measured using VTIR spectroscopy (Table 5).
(22) TABLE-US-00006 TABLE 5 Dissociation temperatures of IPDI blocked with a range of acetophenone oxime analogues that possess electron withdrawing or electron donating groups at the ortho, meta or para positions. Dissociation Temperature Blocking Group (° C.) 5.23
(23) The dissociation temperature appeared to be significantly reduced by the presence of an electron withdrawing group at the para-position 5.23. The presence of an ortho nitro-substituent did not reduce the dissociation temperature.
(24) Curing Studies of HTPB Using Oxime-Urethanes
(25) The potential of the generated oxime-urethanes 5.12 to 5.28 to cure HTPB was investigated. Each oxime-urethane (8.01 mmol) was mixed with HTPB (18.22 g) and DBTDL (0.044 g) in ratios according to the Rowanex 1100 formulation using an overhead stirrer at 70° C. All aliphatic oxime-urethanes exhibited excellent solubility in HTPB at 70° C., thus complete dispersion was achieved. In contrast, all of the aromatic oxime-urethanes exhibited poor solubility at 70° C. and uniform dispersion of 5.15, 5.16 and 5.23 could only be achieved at high temperatures (>100° C.) with vigorous mixing. Uniform dispersion of all of the other aromatic oxime-urethanes was not achieved.
(26) The mixtures were heated to 120° C. for a period of 72 hours in an evacuated atmosphere. Cured HTPB was afforded successfully using sterically encumbered aliphatic oxime-urethanes 5.13 and 5.14. The generation of a polyurethane matrix was achieved using 5.15, 5.16 and 5.23, however, the poor solubility of these oxime-urethanes led to separation from the polymer and the formation of crystallised regions was observed. The poor solubility of aromatic oximes 5.24 to 5.28 prevented the formation of a polyurethane matrix and only curing small regions of HTPB.
(27) TABLE-US-00007 TABLE 5.6 Solubility and curing capability of oxime-urethanes 5.12-28 in HTPB. Soluble in Cure of Blocking group HTPB (70° C.) HTPB (120° C.) 5.12 2-Butanone oxime yes no 5.13 3-Methyl-2-butanone oxime yes yes 5.4 3,3-Dimethyl-2-butanone yes yes oxime 5.14 2,4-Dimethyl-3-pentanone yes yes oxime 5.15 Acetophenone oxime no yes 5.16 Benzophenone oxime no yes 5.23 o-Methoxyacetophenone no yes oxime 5.24 m-Methoxyacetophenone no no oxime 5.25 p-Methoxyacetophenone no no oxime 5.26 o-Nitroacetophenone oxime no no 5.27 m-Nitroacetophenone oxime no no 5.28 p-Nitroacetophenone oxime no no
Monitoring the Curing of HTPB
(28) A variety of techniques can be employed to monitor the reaction of curing polyurethanes. These include 1H NMR spectroscopy, IR spectroscopy, differential scanning analysis (DSC), swelling behaviour and tensile testing.
(29) As a result of the high molecular weight and restricted mobility of the polymer chains in curing HTPB, traditional methods for observing chemical reaction using 1H NMR spectroscopy is restricted. In addition, the elastomeric nature of the cured material prevented the preparation of a fine powder required for solid state NMR techniques.
(30) In an IR spectrum, isocyanates exhibit a stretching vibration that appears as an absorption at 2250 cm-1, thus observing the appearance of this characteristic absorption upon dissociation of the blocked isocyanate followed by its disappearance as the crosslinking reaction reaches completion could be an effective method for monitoring the curing reaction. However, no absorption corresponding to the isocyanate was observed during curing, suggesting the reaction occurred immediately upon the dissociation of the blocked isocyanates.
(31) As the curing reaction ensues, the crosslinking density in turn also increases, this may be observed by an increase in the glass transition temperature Tg as the mobility of the polymer chains decreases. However, the glass transition of the fully cured polyurethane was below the detectable limits of DSC or indeed the high crosslinking density prevented the observation of a defined transition.
(32) Tensile testing offers a route to monitor the curing reaction, as the curing reaction ensues and the crosslinking density increases, the elastic modulus (=□stress/□strain) is expected to increase. Tensile testing of the curing mixture of HTPB and 5.4 was measured at 24, 48 and 72 hours at 120° C. In addition, tensile testing was performed on a control polyurethane generated from IPDI, HTPB and DBTDL cured for 72 hours at 60° C. An increase in the elastic modulus was observed after 48 hours and a small increase was observed after 72 hours, suggesting the majority of the curing had occurred within 48 hours at 120° C. The elastic modulus of cured control polyurethane was significantly higher than the 5.4 mixture. A plasticising effect of the released oxime may account for this change in elastic modulus.
(33) Benzophenone Oxime-Blocked HTPB Based Prepolymer
(34) Benzophenone oxime and IPDI were reacted in a ratio of 1:2, this ensured a mixture of IPDI, mono-blocked IPDI and di-blocked IPDI was generated. To this mixture, HTPB and DBTDL were added in order to afford an oligomeric mixture that contains benzophenone oxime-blocked HTPB based prepolymer
(35) ##STR00040##
Structure of Benzophenone Oxime-Blocked HTPB Based Prepolymer 5.29.
(36) The oligomeric mixture 5.29 was cured at 120° C. for a period of 72 hours and a uniformly crosslinked polyurethane was generated successfully. Swelling tests revealed that the complete crosslinking was achieved after 72 hours
Synthesis of o-Nitroacetophenone Oxime Blocked-IPDI 5.26
(37) ##STR00041##
(38) Isophorone diisocyanate (7.13 g, 32.1 mmol) and o-nitroacetophenone oxime 5.20 (11.55 g, 64.1 mmol) were dissolved in THF (100 mL) and maintained under reflux for 18 hours under an atmosphere of argon. The solvent was removed to leave a pale yellow coloured solid 5.26 (18.65 g, 100%) (m.p. 78-80° C.). 1H NMR (400 MHz, CDCl.sub.3) □H (ppm): 0.94 (3H, s, CH3), 1.00 (1H, m, CH2), 1.00 (1H, m, CH2), 1.06 (1H, m, CH2), 1.08 (3H, s, CH3), 1.09 (3H, s, CH3), 1.22 (1H, m, CH2), 1.75 (1H, m, CH2), 1.79 (1H, m, CH2), 2.38 (3H, s, CH3), 3.03 (2H, m, CH2), 3.92 (1H, m, CH), 5.95 (1H, m, NH), 6.20 (1H, m, NH), 7.47-7.74 (6H, m, 6×CH), 8.01-8.22 (2H, m, 2×CH); 13C NMR (100 MHz, CDCl.sub.3) □C (ppm): 17.4, 21.6, 23.1, 27.4, 31.9, 34.8, 36.5, 41.3, 45.0, 46.2, 46.9, 54.8, 124.7, 128.1, 130.1, 130.6, 131.3, 131.7, 133.6, 133.7, 134.4, 145.6, 147.7, 154.0, 155.3, 160.0; FTIR (ATR) □ (cm-1): 3411 (N—H), 2954 (C—H), 1731 (C═O), 1612 (C═N), 1525 (N—O), 1499 (C—N), 1028 (C—O), 993 (C—O), 913 (N—O); ESIMS calculated mass (C28H34O8N6Na)+605.2330 found 605.2328.
Synthesis of m-Nitroacetophenone Oxime Blocked-IPDI 5.27
(39) ##STR00042##
(40) Isophorone diisocyanate (7.05 g, 31.7 mmol) and m-nitroacetophenone oxime 5.21 (11.43 g, 63.4 mmol) were dissolved in THF (100 mL) and maintained under reflux for 18 hours under an atmosphere of argon. The solvent was removed to leave a pale yellow coloured solid 5.27 (18.65 g, 100%) (m.p. 78-80° C.). 1H NMR (400 MHz, CDCl.sub.3) □H (ppm): 1.00 (3H, s, CH3), 1.10 (1H, m, CH2), 1.10 (1H, m, CH2), 1.13 (3H, s, CH3), 1.15 (1H, m, CH2), 1.17 (3H, s, CH3), 1.30 (1H, m, CH2), 1.85 (1H, m, CH2), 1.89 (1H, m, CH2), 2.50 (3H, s, CH3), 3.14 (2H, m, CH2), 4.03 (1H, m, CH), 6.07 (1H, m, NH), 6.45 (1H, m, NH), 7.65 (1H, m, CH), 8.03 (1H, m, CH), 8.32 (1H, m, CH), 8.54 (1H, m, CH); 13C NMR (100 MHz, CDCl.sub.3) □C (ppm): 14.5, 23.11, 27.7, 32.0, 34.7, 36.8, 41.5, 45.1, 46.0, 47.2, 54.8, 121.7, 124.9, 129.9, 132.5, 136.6, 148.4, 154.0, 155.3, 158.2; FTIR (ATR) □ (cm-1): 3408 (N—H), 2953 (C—H), 1727 (C═O), 1623 (C═N), 1528 (N—O), 1498 (C—N), 994 (C—O), 929 (N—O); ESIMS calculated mass (C28H34O8N6Na)+605.2330 found 605.2329.
Synthesis of p-Nitroacetophenone Oxime Blocked-IPDI 5.28
(41) ##STR00043##
(42) Isophorone diisocyanate (7.33 g, 32.0 mmol) and p-nitroacetophenone oxime 5.22 (11.88 g, 65.9 mmol) were dissolved in THF (100 mL) and maintained under reflux for 18 hours under an atmosphere of argon. The solvent was removed to leave a pale yellow coloured solid 5.28 (19.21 g, 99%) (m.p. 81-85° C.). 1H NMR (400 MHz, CDCl.sub.3) □H (ppm): 0.99 (3H, s, CH3), 1.08 (1H, m, CH2), 1.09 (1H, m, CH2), 1.12 (3H, s, CH3), 1.14 (1H, m, CH2), 1.15 (3H, s, CH3), 1.29 (1H, m, CH2), 1.83 (1H, m, CH2), 1.90 (1H, m, CH2), 2.49 (3H, s, CH3), 3.13 (2H, m, CH2), 4.01 (1H, m, CH), 6.04 (1H, m, NH), 6.40 (1H, m, NH), 7.86 (2H, AA′XX′ system, 2×CH), 8.29 (2H, AA′XX′ system, 2×CH); 13C NMR (100 MHz, CDCl.sub.3) □C (ppm): 14.4, 22.8, 27.6, 32.0, 35.0, 36.7, 41.6, 45.1, 45.8, 47.3, 54.8, 123.9, 127.8, 140.8, 148.9, 153.9, 155.3, 158.7; FTIR (ATR) □ (cm-1): 3405 (N—H), 2953 (C—H), 1727 (C═O), 1594 (C═N), 1516 (N—O), 1497 (C—N), 993 (C—O), 921 (N—O); ESIMS calculated mass (C28H34O8N6Na)+605.2330 found 605.2329.
Synthesis of Benzophenone-Blocked HTPB Prepolymer 5.29
(43) ##STR00044##
(44) IPDI (17.8 g, 8.0 mmol) and benzophenone oxime (0.808 g, 4.1 mmol) were dissolved in THF (100 mL) and maintained under reflux for a period of 18 hours under an atmosphere of argon. The solution was added to a mixture of hydroxy-terminated polybutadiene (HTPB) (18.22 g) and DBTDL (0.044 g, 0.07 mmol) and maintained under reflux for a further period of 18 hours. The solvent was removed in vacuo to give a pale yellow coloured viscous oil 5.29 (21.03 g, 100%). FTIR (ATR) □ (cm-1): 3007 (C—H), 2915 (C H), 2844 (C—H), 1714 (C═O), 1639 (C═N), 1511 (C—N), 1216 (C—N), 965 (C—O) 911 (N—O), 754 (C═C); GPC (THF, BHT 250 ppm): Mn=12718 Da, Mw=76566 Da, Ð=6.02.
(45) An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings of which:—
(46)
(47) Turning to
(48) It should be appreciated that the compositions of the invention are capable of being incorporated in the form of a variety of embodiments, only a few of which have been illustrated and described above.