2.2- dibutyl-2-stanna-l,3-dioxepane

Kricheldorf HR, Eggerstedt S (1998) Macrocycles 2. Living macrocyclic polynnerization of e-caprolactone with 2,2-dibutyl-2-stanna-l,3-dioxepane as initiator. Macromol Chem Phys 199 283-290... 

Kricheldorf and coworkers have found that some heterocyclic compounds containing two reactive bonds behave as bifunctional reactants in a ROP that proceeds by a step polymerization mechanism [Kricheldorf, 2000]. An example is the polymerization of 2,2-dibutyl-2-stanna-l,3-dioxepane with an aliphatic diacid chloride ... 

Kricheldorf et al. reported an anionic polymerization of y-D,L-butyro-lactone or D,L-lactide with cyclic dibutyltin initiators, such as 2,2-dibutyl-2-stanna-l,3-dioxepane, to give cyclic polymers [ 138-140]. Figure 41 shows the ring expansion polymerization of lactone for synthesizing a cyclic polymer as an example. They also synthesized the cyclic polymer with a living mechanism in the polymerization of e-caprolactone [141]. 

Kricheldorf s group demonstrated that 2,2-dibutyl-2-stanna-l,3-dioxepane (DSDOP) could be used as cyclic initiator for the polymerization of TMC (Scheme 44).2 3,234 polymerizations were either conducted in concentrated chlorobenzene solution at 50 and 80 °C or in bulk at 60 and 120 °C. 

The dispersion polymerizations of s-caprolactone and lactides were initiated with initiators used for initiation of polymerizations of the above-mentioned monomers in solution. Diethylaluminum ethoxide, stannous 2-ethylhexano-ate, ° stannous 2-ethylhexanoate/polyalcohols, and 2,2-dibutyl-2-stanna-l,3-dioxepane were used for the dispersion polymerizations of lactides. The dispersion polymerizations of 8-caprolactone were initiated with diethylaluminum ethoxide and sodium trimethylsilano-late. Of the above-mentioned initiators, only the latter one initiated the anionic polymerization. 

When 2,2-dibutyl-2-stanna-l,3-dioxepane ((a) in Formula 9.2) was mixed with bisphenol-A bis-chloroformiate, again an exothermic reaction took place, and polycarbonates having corrected Mns up to 30 kDa with PDs around 1.5 were obtained [32] (see Formula 9.4). Due to the fact that the Sn-S bond is... 

Two different kinds of copolycondensations should be mentioned First, it was demonstrated by the author that a mixture of 2,2-dibutyl-2-stanna-l,3-dioxepane and silacycle (o), n = 2, (see Formula 9.5) is suitable for RO-PC with... 

Ring-expansion polymerization-which is also known as macrocyclic polymerization (as developed by Kricheldorf and Hauser [15])-uses initiators such as 2,2-dibutyl-2-stanna-l,3-dioxepan (DSDOP) (see Scheme 5.4). 

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