Open anion

Lactomes may also be polymerized by ring-opening anionic polymerization techniques. While the five-membered ring is not readily cleaved, the smaller rings polymerize easily producing linear polyesters (structure 5.46). These polymers are commercially used as biodegradable plastics and in PU foams. 

Graft copolymer, polyclhylene-gra/f-poly(propylcnc oxide) (PE-g-PPG), has been synthesized by ring opening anionic polymerization of propylene oxide with a phosphazene catalyst and hydroxylated polyethylene (Mn = 12400, [OH] = 5 units/chain). Polymerization of propylene oxide was carried out in tetraline at 120 °C for 20 hours. The 13C NMR analysis of PE-g-PPG suggested that all the hydroxyl groups were consumed for propylene oxide polymerization (Fig. 6). 

Polyclhylcnc-gra/f-polycaprolaclonc (PE-g-PCL) was synthesized by ring opening anionic polymerization of e-CL with a triethylalminum catalyst and hydroxylated PE. Polymerization of e-CL was performed in toluene for 24 hours. The obtained PE-g-PCL, in which 36-80 mol % of the hydroxyl groups worked as initiators for e-CL polymerization, possessed 29 units of e-CL in polymer hybrids (Fig. 7). 

The metalation of telluropyrone (30) with LDA generates the 3-lithio derivative which equilibrates with the ring-opened anion (31). The latter furnishes traces of the tellurophene derivative (32) by Michael addition <88JOC1203>. 

Zeolites are crystalline alumina-silica-based open anionic framework structures with uniformly sized, rigid pores and channels. Incorporation of porphyrins into zeolites has been explored as means to biomimetic oxidation catalysts. " The initial efforts to combine porphyrins with zeolites resulted in materials in which the porphyrins were supported on the external zeolite surfaces rather than encapsulated inside the pores. The first of this type of material was reported by Bedioui and coworkers which the... 

Nylon 5 or poly(Of-piperidone) can be prepared by ring-opening anionic polymerization of valerolactam. The reaction requires very pure monomer to yield a high molecular weight poly-mer ... 

Purification of fecal bile acids by ion-exchange chromatography according to the method of Kuron and Tennent has not given satisfactory results in other laboratories (33). Some of the bile acid metabolites found in the feces were observed to be strongly absorbed to the resin and large volumes of solvent were required for quantitative elution even when the more open anion-exchanger DEAE-Sephadex was used. 

MALDI-tof-ms has been used to study the preparation of linear polysilox-anes with hydride end-capped and cyclic polysiloxanes from the ring-opening anionic polymerization reaction with hexamethylcyclotrisiloxane and octamethylcy-clotrisiloxane (99). The PDMS reaction was followed by MALDI and the incorporation of the hydride end cap and the creation of the cyclics was studied as a function of time. Further studies (100) employed MALDI and sims it was found that MALDI provides more reproducible relative intensities of the n-mers than does SIMS. 

Ring-Opening Anionic Polymerization The Role of Lithium Chloride... 

The same problem of incorporation is also under examination with block copolymer of ethylene oxide and butylene oxide, already quoted above for inisurfs and transurfs, but functionalized with various polymerizable groups such as acrylic, methacrylic, and styrenic. These surfactants are produced by ring-opening anionic polymerization of butylene oxide, initiated by the... 

Ring-opening anionic polymerization is used in the synthesis of polyferroce-nyldimethylsilane (PFS) (see section 9.6.3). This mechanism involves nucleophilic addition of a polymer anion to a cyclic monomer. The monomer then ring opens, leading to incorporation of the monomer into the growing chain and generation of a new anion. This method is not as common as those previously mentioned, but can result in well-defined polymers with unique chemical composition. 

Non-empirical MO calculations for 1,2- and 1,3-dithiolium cations suggest that the d-orbitals are involved in bonding only to a trivial extent. A series of papers has appeared describing CNDO calculations of the electronic spectra of 1,2-dithiolium cations, and presenting a theoretical treatment of the species produced by cathodic reduction of dithiolium salts, particularly the radical form (32). Flash photolysis of 2,5-diphenyl-1,2-dithiolium salts in ethanol yields two products, of which the less stable has the absorption spectrum of the radical (32 R = Ph), and the longer-lived product appears to be the ring-opened anion (33) thus, the reaction is a photoreduction involving solvent. 

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