Poly anionic preparative methods

The MALDI-TOF spectrum of [G-3] poly(benzyl ether) dendrimer-po-ly(ethylene glycol) triblock copolymer shows a broad band of peaks between 4300 and 6100 D with resolution of the individual ethyleneoxide (44 D) units. The MALDI-TOF spectrum of a [G-3] dendrimer with two polystyrene blocks (molecular peak=8073 D) shows material with 6000-11,000 D and a broad band corresponding to material with 2 M+Ag+. SEC can be used to prove that the latter species is indeed an artifact of the mass spectroscopic method. The authors claim almost exact agreement between the polydispersities derived from MALDI-TOF and SEC [40]. This does, however, not leave any room for the unavoidable column spreading in the latter method. Furthermore, anionically prepared low MW polymers have a minimum polydispersity given by (1 + 1/DP) [41]. 

Sulfur-vulcanizable elastomers have been prepared that are designed to reduce hysteresis in tires by reducing the number of polymer free ends. The method for this preparation entails anionically preparing poly(styrene-co-butadiene) using a lithium thioacetal initiator followed by incorporation of a vulcanization agent into the elastomer terminus. 

Poly(ferrocenylsilane)s are high-molecular-weight polymers. The molecular weights of polymers prepared by the thermal ROP range from 10 to 10 with polydispersity indices of 1.5-2.5 [3, 7, 44-46], The molecular weights of the polymers prepared by the anionic polymerization method can be controlled by varying the amount of initiator. Further, polymers with narrow PDFs (less than 1.3) can be obtained by the anionic polymerization [3]. 

The 40-MHz spectrum of two samples of poly(methyl methacrylate) are illustrated in Figure 2.6 (13). The sample marked (a) was prepared via free radical polymerization methods (see Chapter 1). The sample marked (b) was synthesized by a then new method, anionic polymerization. The anionic polymerization method was thought to make samples predominantly isotactic, whereas free radical methods resulted in atactic polymers. 

Fluorinated poly(methacrylates) or poly(acrylates), rich in trifluoromethyl groups, exhibit superior performance of chemical inertness, excellent weatherability, low refractive index, lower dielectric constant, and special surface properties [14,61]. Poly(2,2,2-trifluoroethyl methacrylate), poly(MATRIF), is an important class of such materials. It has been extensively used in high performance coatings [17], photoelectric communications, and microelectronics [62]. Poly(MATRIF) is easily produced by free radical polymerization using bulk, solution, and emulsion polymerization methods [63]. Structural characterization of NMR of poly(MATRIF) prepared by radical and anionic polymerization has been studied. Syndiotactic structure was obtained by radical initiator in contrast to an isotactic structure achieved by anionic polymerization [64]. 

Anionic polymerization of ethylene oxide by living carbanions of polystyrene was first carried out by Szwarc295. A limited number of methods have been reported in the preparation of A-B and A-B-A copolymers in which B was polystyrene and A was poly(oxyethylene)296-298. The actual procedure was to allow ethylene oxide to polymerize in a vacuum system at 70 °C with the polystyrene anion initiated with cumyl potassium in THF299. The yields of pure block copolymers are usually limited to about 80% because homopolymers are formed300. ... 

Analogous principles should apply to ionically propagated polymerizations. The terminus of the growing chain, whether cation or anion, can be expected to exhibit preferential addition to one or the other carbon of the vinyl group. Poly isobutylene, normally prepared by cationic polymerization, possesses the head-to-tail structure, as already mentioned. Polystyrenes prepared by cationic or anionic polymerization are not noticeably different from free-radical-poly-merized products of the same molecular weights, which fact indicates a similar chain structure irrespective of the method of synthesis. In the polymerization of 1,3-dienes, however, the structure and arrangement of the units depends markedly on the chain-propagating mechanism (see Sec. 2b). 

Values for RU differed by up to 100% with 1,4-DVB-microgels [286]. The reliability of methods for determining the RU of 1,4-DVB-microgels was checked [287] with poly(4-vinylstyrene) which was prepared by anionic polymerization of 1,4-DVB (Table 3). From these results, it can be concluded that only quantitative IR-spectroscopy is a reliable method for determining the RU of 1,4-DVB-... 

During the last 5 years, there have been several reports of multiblock copolymer brushes by the grafting-from method. The most common substrates are gold and silicon oxide layers but there have been reports of diblock brush formation on clay surfaces [37] and silicon-hydride surfaces [38]. Most of the newer reports have utilized ATRP [34,38-43] but there have been a couple of reports that utilized anionic polymerization [44, 45]. Zhao and co-workers [21,22] have used a combination of ATRP and nitroxide-mediated polymerization to prepare mixed poly(methyl methacrylate) (PMMA)Zpolystyrene (PS) brushes from a difunctional initiator. These Y-shaped brushes could be considered block copolymers that are surface immobilized at the block junction. 

As explained in Sections 16.3.4, 6.4.1, and 16.4.2, SEC is a nonabsolute method, which needs calibration. The most popular calibration materials are narrow molar mass distribution polystyrenes (PS). Their molar mass averages are determined by the classical absolute methods—or by SEC applying either the absolute detection or the previously calibrated equipment. The latter approach may bring about the transfer and even the augmentation of errors. Therefore, it is recommended to apply exclusively the certified well-characterized materials for calibrations. These are often called PS calibration standards and are readily available from numerous companies in the molar mass range from about 600 to over 30,000,000g moL. Their prices are reasonable and on average (much) lower than the cost of other narrow MMD polymers. Other available homopolymer calibration materials include various poly(acrylate)s and poly(methacrylate)s. They are, similar to PS, synthesized by anionic polymerization. Some calibration materials are prepared by the methods of preparative fractionation, for example, poly(isobutylene)s and poly(vinylchloride)s. 

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