Energetic ABA and (AB)_n thermoplastic elastomers

Abstract

SYNOPSISLinear ABA triblock and ( AB ), segmented block copolymers of energetic monomers have been synthesized. The rigid and soft blocks are prepared from 3,3-bis( azidomethyl) oxetane (BAMO) and 3-nitratomethyl-3-methyloxetane (NMMO) , respectively. Polymerization of BAMO initiated by triethyloxonium tetrafluoroborate and by spiro (benzoxasilole) /propanediol produced a-monohydroxy-PBAMO ( 3) and a,w-dihydroxy-PBAMO ( 4 ) of @" 16,000 and 2,000, respectively, and a,w-dihydroxy-PNMMO ( 5 ) of M,, = 13,000 was synthesized by the latter method. The block copolymers were prepared from the appropriate telechelic polymers and toluene diisocyanate. The PBAMO-PNMMO-PBAMO copolymer 6 has T , = 8Z°C, T, = -3"C, and is strongly phase separated even in the melt. It decomposes sharply within 1°C a t 224OC evolving 0.69 kJ/g of heat. Copolymer 6 has excellent mechanical properties with elongation of 683% at break, 5.25 MPa stress, and 82% recovery.The ( PBAMO-PNMMO ), , copolymer 7 has similar thermal properties and spectroscopic characteristic, but is inferior to copolymer 6 in all rheological and mechanical properties. INTRODUCTIONThermoplastic elastomers (TPE) are useful materials.' They can be prepared from any combination of low Tg building block with high Tg or crystalline ones. Segmented TPE is prepared by coupling the appropriate telechelic prepolymer in equal molar ratio. Linear ABA triblock copolymer can be elegantly synthesized by sequential polymerization if living propagation of all the constituent monomers can be achieved. It is more readily prepared by coupling telechelic low Tg prepolymer with monofunctional high Tg/ crystalline prepolymer as the terminal hard blocks. The synthesis of these functional prepolymers are prerequisite for this route. TPE containing energetic groups have been considered to be binder for propellent. The central purpose of this research is to synthesize both segmented and ABA TPE's from energetic monomers.It has been reported that 3,3,3',3'-tetrakis- Though living polymerization was not achieved for these oxetanes, a,w-dihydroxypolymer was obtained with 1 /propandiol. Furthermore, a-monohydroxypolyoxetanes was synthesized using either the 1 / benzyl alcohol catalyst or the Et30+BF; initiator.We present here the synthesis of TPE from these prepolymers and their properties.* To whom correspondence should be addressed. Polymerization and block coupling reactions were performed using dry argon purged Schlenk type apparatus. The crystalline block 3 was synthesized by BAMO, catalyst 2, and methylene chloride in the desired ratios were mixed and stirred at 25°C. The polymerization was quenched with water and the white powdery polymer 3 was precipitated with tenfold excess of aqueous NH3 in methanol. a,w-Dihydroxy PoIy(NMM0) (5)The telechelic amorphous block 5 was also prepared using catalyst 1 and propanediol: NMMO (9.9 g, 67 mmol), propanediol (0.5 g, 7 mmol), and 1 (0.3 g, 0.59 mmol) were combined and reacted for 3 days. The product was washed with an equal volume of aqueous methanol th...

Synthesis and characterization of poly(3,3 bis(azidomethyl)oxetane-co-?-caprolactone)s

“…[1][2][3][4][5][6][7][8][9] Suitable TPEs can also be prepared by coupling a telechelic low T g prepolymer with a monofunctional high T g or crystalline prepolymer as the terminal hard blocks. 5 Linear ABA triblock copolymers can also be synthesized by sequential polymerization if the living polymerization of the corresponding two monomers can be achieved. 4,6,7 Cyclic ethers and oxetane derivatives are known to polymerize cationically and are usually initiated by a cocatalysis in the presence of a Lewis acid, such as BF 3 .…”

Review on Energetic Thermoplastic Elastomers (ETPEs) for Military Science

“…B. Xu et al synthesized ABA and (AB) n type copolymers of BAMO and NIMMO [16]. First a-mono hydroxyl poly-BAMO was prepared by using Et 3 OBF 4 (triethyl oxonium tetrafluoroborate) initiator at 25 8C and the telechelic poly-BAMO and poly-NIMMO were synthesized by using the catalyst 3,3,3',3'-tetrakis (trifluoromethyl)-1,1'-(3H,3H 1 )-spirobis(2,1-benzoxasilole) (structure given in Figure 4) and a diol initiator (butane diol or propane diol).…”

Energy‐Intensive Random Block Copolymers of 3,3‐Bis (Nitratomethyl) Oxetane and 3‐Azidomethyl‐3‐ Methyloxetane

“…Boron trifluoride etherate [26], p-bis (a, a-dimethylchloromethyl) benzene together with co-catalyst (AgSbF6) [21], (trifluoromethyl)-1,1'-(3H,3H1)-spirobis(2,1-benzoxasilole) [28] have recently been used as catalysts of the ringopening polymerization reaction.…”