Protected functionalized initiators for

Other workers have recognized the benefit of using our protected hydroxyl initiators. For example, Teyssie has successfully used (II) to prepare narrow MWD terminated polysiloxanes with good Hn control and high functional purity, (Eq. 10, 11) (Table V)(49). 

Protecting groups have been used in several ways for the preparation of functional anionic polymers e.g. as protected functional initiators, terminating agents, and monomers. Scheme 1 illustrates these methods. 

FMC has supplied -butyllithium and -butyllithium as initiators for anionic polymerization for over thirty years. The utility of this family of protected functional initiators to prepare telechelic polymers was intriguing. The retrosynthesis of 6- r-butyldimethylsilyloxy)-l-hexyllithium is illustrated in Figure 3. In addition, FMC was basic in... 

The synthesis of a miktoarm star copolymer of the type AnBn has been also demonstrated. The synthesis was performed via ATRP using divinylbenzene, as the core cross-liking agent. PEO macroinitiator chains were utilized for the polymerization of divinylbenzene forming a star polymer, with a random number of branches. The above star polymer was used as a multi-functional initiator for the polymerization of methacrylate monomers. Therefore, the synthesis of an amphiphilic miktoarm star copolymer was realized [54]. Finally, the hydrolysis of the protected methacrylate block led to the preparation of the desired DHBCs, namely the PEOn-PMAA stars. SEC analysis of the preeursor PEOn-PMMA copolymer revealed a relatively broad molecular weight distribution. Nevertheless, this is a good example for the synthesis of A Bn double hydrophilic star copolymers. 

In a recent example, Maynard and coworkers demonstrated the synthesis of a Boc-protected aminooxy functionalized initiator for copper(i)-mediated ATRP of NIPAM (Figure 1.8). Deprotection of the polymer end groups... 

The effects of ozone appear to be cumulative for initial exposures followed by adaptation. Five of six subjects exposed to 0.5 ppm ozone 2 hours/day for 4 days showed cumulative effects of symptoms and lung function tests for the first 3 days, followed by a return to near control values on day 4." In animals exposure to 0.3-3 ppm for up to 1 hour permits the animals to withstand multilethal doses for months afterwards. However, repeated exposures impart protection from all forms of lung injury (e.g., susceptibility to infectious agents, enzyme activities, inflammation). Initial ozone exposure may act to reduce cell sensitivity and/or increase mucus thickness, factors which may modify the accessibility and action of the gas. It is not known how variations in the length, frequency, or magnitude of exposure modify the time course for tolerance. 

This reaction can also be utilized to prepare functionalized initiators by reaction of butyllithium with a substituted 1,1-diphenylethylene derivative. For example, polymers end functionalized with primary amine, tertiary amine, phenol, and bis(phenol) groups have been prepared in essentially quantitative yield by using the reaction of butyllithium with the corresponding substituted (or protected) 1,1-diphenylethylene (87). 

Recently, a functional initiator method has been reported for isobutene, where the initiator is CHsOQO)—Ar—C(CH3)2—Cl (Ar = t-BuC6H3) [156]. In the presence of TiCl4 (activator) and N,N-dimethylace-tamide (as an added nucleophile), the cumyl-type moiety of the initiator initiates living cationic polymerization the acetate moiety serves as the protected carboxylic acid. 

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