Hexamethylene carbonate

Lipase CA catalyzed the polymerization of cyclic dicarbonates, cyclobis (hexamethylene carbonate) and cyclobis(diethylene glycol carbonate) to give the corresponding polycarbonates [105]. The enzymatic copolymerization of cyclobis(diethylene glycol carbonate) with DDL produced a random ester-carbonate copolymer. As to enzymatic synthesis of polycarbonates, reported were polycondensations of 1,3-propanediol divinyl dicarbonate with 1,3-propanediol [110], and of diphenyl carbonate with bisphenol-A [111]. 

Table 11.1.3. Compounds identified in the pyrogram of a poly(hexamethylene carbonate) diol sample with M = 860 as shown in Figure 11.1.2.

Another example shown in Figure 11.1.5 is the spectrum for the peak eluting at 111.57 min. in the pyrogram of poly(hexamethylene carbonate). 

The large retention time of the compound generating the spectrum shown in Figure 11.1.5 indicates that it may belong to 6-hydroxyhexyl carbonate, or to a dimer with an OH group, or to a trimer of the hexamethylene carbonate. The ion with m/z = 145 is likely to be the homolog of the ion generating the ion m/z = 133 in the spectrum of carbonic acid dipentyl ester. The tentative structures of the ions with m/z =145 and m/z = 163 are shown below ... 

Cyclic dicarbonates, cyclobis(hexamethylene carbonate) and cyclobis(diethylene glycol carbonate), were polymerized by lipase CA.188 The random ester-carbonate copolymers were enzymatically obtained from DDL-cyclobis(diethylene glycol carbonate) and lactides-TMC.189... 

Figure 1.3 The 300 MHz spectrum oflow molecular weight poly(hexamethylene carbonate)...

Figure 1.5 75.5 MHz spectra of poly(hexamethylene carbonate) in CDCI3. (a) H-coupled spectrum (b) spectrum with continuous broadband H-decoupling. For peak labels, see Figure 1.3. The intensity scale in (a) is approximately tenfold greater than that in (b).

Common SS include polyethers, polyesters and polyalkyl glycols with glass transition temperatures in the range of -70°to -30°C. Commonly used macrodiols in the PUs synthesis are polyalkyl-diols, such as polyisobutylene diol [70], polybutadiene (PBU) [20, 71], or oligo-butadiene diols [72] as well as hydrogenated polybutadiene diol [20] polyether diols polytetrahydrofuran (PTHF or PTMO) [50-52], polyethylene glycol (PEG) or (PEO) [73], polypropyleneoxide (PPO) [73] or mixed blocks of them PEO-PPO-PEO [74] and PPO-THF [54] polyester diols poly(ethylene adipate) (PEA) [4,20], poly(butylene adipate) (PBA) [20, 73], and latterly polycaprolactone diol (PCL or PCD) [75], polyalkylcarbonate polyol [20] or mixed blocks of them, for example poly(carbonate-co-ester)diol [76], poly(hexamethylene-carbonate)diol [77], as well as poly(hexamethylene-carbonate-co-caprolactone)diol [78] and a mixed block copolymer of polyether and polyester blocks PCL-b-PTHF-b-PCL [79]. Examples schemes of macrodiols are shown in Eig. 1.9. 

Such as the previously described, poly(p-dioxanone-co-alkylene oxide) copolymers, bioabsorbable copolymers comprising linkages other than esters have been prepared. Unless one views carbonates as esters of carbonic acid, this w ould also include the family of pohoners based upon p-dioxanone and AA-BB q pe poly(alkylene carbonate )s such as poly(hexamethylene carbonate) (Bezwada, Shalaby and Hunter, 1991) (Figure 12). 

Hence, a prepolymer of poly(hexamethylene carbonate) was formed by adding to a flame dried 250 ml single neck flask 36.6 g of 1,6-hexanediol and 69.2 g of diphenyl carbonate. The flask was fitted with a mechanical stirrer, a distillation adapter and recehing flask. The reaction flask was held under high vacuum at room temperature... 

The resulting poly(hexamethylene carbonate) was cooled to room temperature under a stream of nitrogen, isolated, ground, and dried under vacuum (0.1 mm Hg). The polymer had an I.V. of 0.38 dL/g. 

Five grams of the poly(hexamethylene carbonate) was then added to a flame dried 100 ml two-neck flask, equipped with an overhead stirrer and nitrogen inlet, and dried at 60°C and 0.1 mm Hg for 24 hours. p-Dioxanone (20 g (0.196 mole)) and 0.02 ml of stannous octoate (0.33 molar in toluene) were then added to the flask and held under high vacuum (0.1 mm Hg) at room temperature for an additional 24 hours. The flask was then placed in an oil bath at 110°C. After 15 minutes, the stirred solution became homogenous and began to increase in viscosity. Stirring was continued for 8 hours under nitrogen. 

Poly(ether urethanes) are of special interest due to their good mechanical properties, broad synthetic possibilities, and rather good blood compatibility for medical applications, e.g. catheters, heart valves [47]. A poly(carbonate urethane) (PCU) comprising poly(hexamethylene carbonate), the aromatic diisocyanate 4,4 -diphenylmethane diisocyanate (MDI) and 1,4-butanediol as chain prolonger has been developed (Table 2) [133]. 

Cyclobis- (hexamethylene carbonate) Candida antarctica lipase M = 12,000, DP = 1.7 using SEC analysis against a polystyrene standard. Reaction time 72 h, yield 85% at 60 °C [60]... 

Cyclic dicarbonates, cyclo /s(hexamethylene carbonate) and cyclo /s(diethylene glycol carbonate) were polymerised by lipase from C. antarctica and P. fluorescens [62]. CALB was used for the ROP of cyclo /s(decamethylene carbonate) (DMC2) giving a polymer with a MW of 5.4 x 10 and 99% yield, and an ultralow enzyme/substrate weight ratio of 1/200. Compared with six-membered trimethylene carbonate, a much lower reaction activity of large-sized DMC2 vvas observed, the opposite of the enzymatic polymerisation of lactones with different ring sizes [63]. 

Chemical catalysts such as stannous octanoate, methylaluminoxane and aluminium isopropoxide have been used for the copolymerisation of TMC and 15-pentadecanolide (PDL), and the results showed that TMC had much greater reactivity than PDL. In contrast, for the Novozyme-435-catalysed copolymerisation, PDL had a greater reactivity than TMC. Cyclic dicarbonates, cyclo/ /s(hexamethylene carbonate) and cyclo/ 2s(diethylene glycol carbonate) have been copolymerised with e-CL and 12-dodecanolide (DDL) using CAL in toluene at 60 °C for 48 h (Scheme 12.12) [62]. 

Polymer (B) Characterization a,(Q-dihydroxy poly(hexamethylene carbonate) M /g.mor = 2410 1989ED1... 

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