Organic Chemistry of Explosives

116 Synthetic Routes to Nitrate Esters

O

H 3 C CH 2 ONO 2

HO O

H 3 C CH 2 ONO 2

H

n

122

Poly[NIMMO]

43

(NIMMO)

Figure 3.54

3-Nitratomethyl-3-methyloxetane (NIMMO) (43) is synthesized from the selective nitration

of the hydroxy group of 3-hydroxymethyl-3-methyloxetane with dinitrogen pentoxide in an

inert solvent.36aThe cationic polymerization of NIMMO using an initiator system of boron

trifluoride and a diol yields the energetic polymer poly[NIMMO] (122).^37 Poly[NIMMO]

generated by this process is a viscous liquid with a very low sensitivity to impact and well

suited for use as an energetic binder for rocket propellants and plastic bonded explosives

(PBXs). The synthesis and scale-up of NIMMO and its polymerization to poly[NIMMO] was

pioneered by chemists at DERA (British Defense Evaluation and Research Agency). Chemists

at DERA have also developed a plastic bonded explosive called CPX-413 which is based on

poly[NIMMO]/HMX/NTO/plasticizer and is ranked as an extremely insensitive detonating

substance (EIDS).

O

O

R

O

OH

ONO 2 O 2 NO

H

ONO 2

O

nn

123

Poly[GLYN]

19

(GLYN)

Figure 3.55

Glycidyl nitrate (GLYN) (19) is synthesized in high yield and purity from the selective nitra-

tion of glycidol with dinitrogen pentoxide in an inert solvent.^35 ,^36 The cationic polymerization

of glycidyl nitrate is more difficult than the polymerization of NIMMO and requires a strong

mineral acid like tetrafluoroboric acid.^37 The product, poly[GLYN] (123), is a low molecu-

lar weight hydroxy-terminated pre-polymer which reacts with diisocyanates to give energetic

polyurethane polymers.^164 Willer and co-workers^165 have reported on an improved process

for producing poly[GLYN] which is well suited for use as an oligomer in solid high-energy

compositions. Willer and co-workers^166 have also described the use of low molecular weight

poly[GLYN] for use as an energetic plasticizer. In this context, poly[GLYN] has a number of ad-

vantages over traditional nitrate ester plasticizers, including: low volatility, lowTg(∼− 40 ◦C),

excellent miscibility with the binder and decreased plasticizer mobility. On the basis of perfor-

mance and the ease with which poly[GLYN] is prepared via dinitrogen pentoxide technology,

it seems likely that it will prove to be a world leader in the field of energetic polymers.

Recent interest has turned to nitrated cyclodextrin polymers (poly-CDN) for potential use

in insensitive and minimum smoke producing propellants.^167 The synthesis, purification and

characterization of the following polymers was studied in detail:^168

(1) r-Cyclodextrin polymer cross-linked with 1-chloro-2,3-epoxypropane.

(2) r-Cyclodextrin polymer cross-linked with 4,4′-methylene-bis(phenyl isocyanate).