Ring opening polymerization thermal

As early as 1895, the synthesis of polydichlorophosphazene was attempted by H.N. Stokes by thermal ring-opening polymerization of hexachloro-triphosphazene [(NPCl2)3]. The product obtained by H.N. Stokes was a high-molecular weight cross-linked rubbery material called inorganic rubber which is insoluble in all solvents and hydrolytically decomposes into phosphates, ammonia, and hydrochloric acid in the presence of moisture. Because of its insolubility and hydrolytic instability, the polymer found no technological application and remained as a laboratory curiosity. 

In 1964, H.R. Allcock filed a patent claiming the preparation of a soluble polydichlorophosphazene. The polymer obtained can be soluble in organic solvents such as benzene and toluene. This thermal ring-opening polymerization of hexachloro-triphosphazene in the melt at 250°C is the most fully developed and commonly used method for polydichlorophosphazene synthesis to date. 

Also of interest are the thermal ring opening polymerizations of 1,1-dimethyl-l-silabenzocyclobutene (eq. 10) [50] and of 1,1,2,2-tetramethyl-1,2-disilabenzocyclobutene (eq. 11) [51]. The polymer produced in the latter reaction is a polycarbodisilane. 

The hybrid polymer 140 is generated by a thermal ring-opening polymerization (ROP) process (Scheme 10).300,301 Polymers containing three-coordinate sul-fur(IV) are generally hydrolytically sensitive even when the chloro substituents are replaced by phenoxy groups.302... 

The cyclolinear polycarbosilane, (poly(l-hexyl-l,3-ditolyl-l,3-disilacyclobutane), prepared by ADMET polymerization as reported previously (see Scheme 13) was modified by grafting poly(methyl methacrylate) (PMMA) or polystyrene <2006MM8684>. Polydiphenylsilylenemethylene thin films have been synthesized by using laser-ablated metal nanoparticles for the thermal ring-opening polymerization of l,l,3,3-tetraphenyl-l,3-disilacyclobutane <2007MI3093>. 

Scheme 1. Proposed mechanism for the thermal ring-opening polymerization (ROP) of cyclic thionylphosphazenes (18 and 20)...

Thermal ring-opening polymerization of 63 [157b] A sample of the monomer 63 (450 mg, 1.51 mmol) was flame-sealed in an evacuated (0.01 mm Hg) Pyrex tube and heated at 150 °C for 3 h. The tube contents were dissolved in THE, filtered, and precipitated into methanol. The fibrous orange solid of 64 was filtered off, washed with methanol (3x5 mL), and dried under vacuum. Yield 340 mg (75%). = 1.2 10 Da. 

FIGURE 11.2 Synthesis of the prepolymer poly(dichlorophosphazene) (b) via thermal ring-opening polymerization of trimer hexachlorocyclotriphosphazene (a) or living cationic polymerization of a phosphoranamine monomer (c). 

The earliest and most well-developed route to polyphosphazenes involves the thermal ring-opening polymerization of cyclic phosphazenes bearing halogen substituents at phosphorus. Use of this method and subsequent halogen replacement with alkoxides has led to the synthesis of ferrocene- and ruthenocene-containing polyphosphazenes (2.20 and 2.21) with molecular weights (M ) in excess of 2 x 10 [49, 50]. 

The main method of synthesis for polyphosphazenes [4-6] involves the thermal ring opening polymerization of monomer 5 to uncrosslinked high polymer 6, followed by solution state nucleophilic replacement of the chlorine atoms in 6 by organic or organometallic side groups. The overall process is illustrated in Scheme I. 

The platinum-catalyzed or thermal ring opening polymerization of the substituted silacyclobutane monomers yields linear polycarbosilanes. The platinum-catalyzed hydrosilations of the AB (allyl) and AB2 (diallyl) monomers yield linear and hyperbranched polycarbosilanes, respectively. A wide range of random copolymers are readily available from polymerization of mixtures of the silacyclobutane or AB and AB2 monomers. The preparation of random copolymers is often of interest for achieving desired physical properties. 

Cyclic, silicon-bridged [l]ferrocenophanes have been found to undergo thermal ring-opening polymerization to afford high-molecular-wei t poly(ferrocenylsilane)s (see Eq. 1.31) [8, 43]. Many other members of this family of polymers are now known including those where the silicon center is replaced by Sn(IV), P(III), Ge(IV), B(III) etc., [8],... 

Thermal Ring-opening Polymerization of Silicon-bridged Ferrocenophanes... 

Thermal ring-opening polymerization of [2]ferrocenophanes has also been reported by Manners and coworkers (20). Oxidation of the polyferrocenylethyl-ene with tetracyanoethylene resulted in antiferromagnetic interactions. Unsymmetric [2]ferrocenophanes (R=S, P) have also been synthesized and ring-opened however, a ferrocenophane containing a C-Si bridge was resistant to thermal, anionic, and transition-metal-catalyzed ROP. " The [2]carbathioferrocenophane could also be polymerized in the presence of cationic initiators. 

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