Poly controlled molecular weight

Poly(dioxaboralane)s (82) (Fig. 51) with controllable molecular weights were reported to be readily obtained through the condensation reaction between 9,9-dihexylflourene-2,7- diboronic acid and pentaerythritol in toluene with an associated azeotropic removal of water. The molecular weights of the resulting polymers, which ranged between 10,000 and 76,900, were found to depend on the processing conditions of the polymers.117... 

GTP was employed for the synthesis of block copolymers with the first block PDMAEMA and the second PDEAEMA, poly[2-(diisopropylamino)e-thyl methacrylate], PDIPAEMA or poly[2-(N-morpholino)ethyl methacrylate], PM EM A (Scheme 33) [87]. The reactions took place under an inert atmosphere in THF at room temperature with l-methoxy-l-trimethylsiloxy-2-methyl-1-propane, MTS, as the initiator and tetra-n-butyl ammonium bibenzoate, TBABB, as the catalyst. Little or no homopolymer contamination was evidenced by SEC analysis. Copolymers in high yields with controlled molecular weights and narrow molecular weight distributions were obtained in all cases. The micellar properties of these materials were studied in aqueous solutions. 

Recently, Kondo and coworkers reported on the polymerization of St with diphenyl diselenides (37) as the photoiniferters (Eq. 39) [ 162]. In the photopolymerization of St in the presence of 37a and 37b, the polymer yield and the molecular weight of the polymers increased with reaction time. The chain-end structure of the resulting polymer 38 was characterized. Polymer 38 underwent the reductive elimination of terminal seleno groups by reaction with tri-n-butyltin hydride in the presence of AIBN (Eq. 40). It also afforded the poly(St) with double bonds at both chain ends when it was treated with hydrogen peroxide (Eq. 41). They also reported the polymerization of St with diphenyl ditelluride to afford well-controlled molecular weight and its distribution [163]. 

Another prime advantage of living free radical procedures is the compatibility of both nitroxide-mediated and ATRP procedures with functionalized monomers. An excellent example of this is the preparation of poly(2-hydroxyethyl methacrylate) with controlled molecular weight and low polydispersity by the ATRP of HEMA (Scheme 13) [40]. In contrast to normal monomers the... 

Moreover, alcohol functionalities have been introduced into the polynor-bornene (PNB) backbone by copolymerization of norbornene with a few percent of 5-acetate norbornene and subsequent acetate reduction. After transformation of the pendant hydroxyl functions into diethyl aluminum alkoxides, sCL has been ring opening polymerized (Scheme 31). Owing to the controlled/ liv-ing character of both polymerization processes the isolated poly(NB- -CL) graft copolymers were characterized by well-defined composition, controlled molecular weight and branching density, and narrow MWD (PDI=1.2-1.4) [92]. 

Y > Sm > Nd) [108]. Neodymium surface species 9 generated by silylamido alkoxo secondary ligand exchange was more efficient in e-CL polymerization, producing well-defined poly(CL)s with controllable molecular weight and polydis-persity [114]. 

In the present section we describe the living anionic polymerization of meth-acrylonitrile by two initiating systems such as the aluminum porphyrin-Lewis acid system and the aluminum porphyrin-Lewis base system which enables the synthesis of poly(methyl methacrylate-h-methacrylonitrile)s of controlled molecular weights. 

Methods for preparing and using compositions containing poly(4-methyl-l-pentene) having a controlled molecular weight distribution are described by Patel et al. (3). Methods for preparing multilayer films and film layers are also described. 

As shown in Eq. (14), poly(arylene ether imide)s were synthesized by the Friedel-Crafts reaction of diphenoxydiimide monomers and iso or terephthaloyl chloride [51], The diphenoxydiimide monomers were readily prepared by the condensation of 4-phenoxyaniline with appropriate aromatic tetracarboxylic dianhydrides. Several poly(arylene ether imide)s of controlled molecular weight (Mn = 40,000 g/mol) prepared by this route are presented in Table 21. As... 

The Cu(II)/Cu(I) redox system added as bromide has recently been used to prepare well-defined polymers (controlled molecular weight, reduced poly-dispersity, terminal functionalities). One of the most successful methods to make well-defined polymers is atom transfer radical polymerisation (ATRP)18 ... 

Cationic polymerizations are not only important commercial processes, but, in some cases, are attractive laboratory techniques for preparing well-defined polymers and copolymers. Polyacetal, poly(tetramethyl-ene glycol), poly(e-caprolactam), polyaziridine, polysiloxanes, as well as butyl rubber, poly(N-vinyl carbazol), polyindenes, and poly(vinyl ether)s are synthesized commercially by cationic polymerizations. Some of these important polymers can only be prepared cationically. Living cationic polymerizations recently have been developed in which polymers with controlled molecular weights and narrow polydispersity can be prepared. 

Since the development of living cationic polymerizations of alkyl vinyl ethers (Chapter 4, Sections IV and V.A), considerable efforts have been made to synthesize and polymerize vinyl ether derivatives carrying polar functional substituents, and thereby it is now possible to obtain a variety of pendant-functionalized poly(viny) ethers) of controlled molecular weights and narrow MWDs [1,2,13], Figure 3 lists typical examples of vinyl ethers carrying various pendant functionalities for which living cationic polymerizations are available [14-35]. These monomers are synthesized most conveniently from 2-chloroethyl vinyl ether, now commercially available,... 

Properties of a specific polymer can often be varied by means of controlling molecular weight, end groups, processing, cross-linking, additives, and so on. Therefore, it is possible to classify a single polymer in more than one category. For example, nylon can be produced as fibers in the crystalline forms, or as plastics in the less crystalline forms. Also, poly(vinyl chloride) and siloxanes can be processed to act as plastics or elastomers. 

Halonitriles 1-31 (X = Cl, Br), unimer models of halogen-capped dormant poly (acrylonitrile), are specifically employed for the polymerization of acrylonitrile with copper halides. Controlled molecular weights and narrow MWDs (MJMn = 1.1 —1.4) are achieved.173 174 The strong electron-withdrawing cy-ano group facilitates the formation of the initiating radical, and may thus be employed for other monomers such as MMA with Fe catalysts74 and styrene with CuCl/L-1.84... 

Recommended initiators for methacrylate polymerizations are 1-24 (X = Br) and 1-25 (X = Cl), both of which are unimer and dimer models of poly(methacry-late) dormant terminals, respectively. For example, PMMA with precisely controlled molecular weights, very narrow MWDs (MJMn — 1.1), and nearly perfect end-capping with halogen was obtained with the 1-25 (X = Cl)/Ru-5/Al(0-7-Pr)3 initiating system.60 197 Alternatively, arenesulfonyl chlorides can lead to well-controlled poly (methacrylate) s with narrow MWDs (MJMn = 1.1 —1.2) in combination with copper catalysts.126176... 

The alkyl substituents of methacrylates are varied as methyl (M-l),27-84-100-132-133 176 ethyl (M-2),102198 isopropyl (M-3),199 n-butyl (M-4),102 132 176 198 isobutyl (M-5),102 sec-butyl (M-6),102 tot-butyl (M-7),63102 isobornyl (M-8),63 2-phenylethyl (M-9),195 benzyl (M-10),199 and 4-nitrophenyl (M-ll)166 methacrylates were also polymerized in a controlled way, and the polymer from M-ll can be converted easily into poly(methacrylic acid) via deprotection of the nitrophenyl group. Sodium methacrylate (M-12), an ionic monomer, can be polymerized directly into poly(methacrylic acid) sodium salt with controlled molecular weights and narrow MWDs (MJMn = 1.2—1.3) with a water-soluble bromide initiator and CuBr/L-1 in water under alkaline conditions (pH 8—9) at 90 °C, although the polymerization stopped around 70— 80%.200... 

Side-chain liquid-crystalline polymers with controlled molecular weights have been obtained by the polymerization of FM-25 with 1-22 (X = Br)/CuBr/ L-3 in the bulk at 100 °C, to examine the thermotropic transition as a function of the MWD.324 Second-order nonlinear optical materials with branched structure were prepared by the copper-catalyzed radical polymerization of FM-26 and FM-27 using hyperbranched poly[4-(chloromethyl)styrene] as a multifunctional initiator.325... 

Combination of a living ionic polymerization and a metal-catalyzed radical polymerization also leads to comb polymers, where both the molecular weights of the arm and main-chain polymers are well controlled. PMMA with poly(vinyl ether) arm polymers of controlled molecular weights (C-l) were prepared by the copper-catalyzed radical polymerization of methacrylate-capped macromonomers carrying a poly-(isobutyl vinyl ether), which were obtained by living cationic polymerization with a methacryloxy-capped end-functionalized initiator.428 Comb polymers with... 

Regioregular Poly(3-alkylthiophenes) with Low POLYDISPERSITIES AND CONTROLLED MOLECULAR WEIGHTS... 

A novel method of producing suspension polymers of poly(vinyl acetate) with a closely controlled molecular weight distribution involves the solution polymerization of vinyl acetate in methanol. By varying the ratio of monomer to methanol, a variety of molecular weight distributions may be prepared. The solution polymer is then added with agitation to an aqueous system containing poly(vinyl alcohol). The methanol is then distilled off to give a bead polymer [121]. 

The investigation, which focused on the use of various chain transfer agents, utilized A -vinylindole, 2-methyl-A-vinylindole and 3-methyl-A-vinylin-dole to synthesize polymers with controlled molecular weights and low poly-dispersities. The photorefractive properties of these polymers were then further investigated. 

Living polymerization of azo monomers is one of the most effective ways to prepare well-defined azo BCs. Generally, a monodispersed macroinitiator should be prepared first. It is then used as an initiator for the subsequent polymerization of azo monomers. Finkelmann and Bohnert (1994) first reported the synthesis of LC-side chain AB azo BCs by direct anionic polymerization of an azo monomer. As shown in Scheme 12.1, the polymerization of polystyrene (PS)-based diblock copolymers was carried out from a PS-lithium capped with 1,1-diphenylethylene (DPE), whereas the poly(methyl methacrylate) (PMMA)-based diblock copolymers were prepared by addition of methyl methacrylate (MMA) monomers to the living azo polyanion, obtained by reaction of l,l-diphenyl-3-methylpentylithium (DPPL) with the azo monomer in tetrahydrofuran (THF) at lower temperature. By this method, a series of well-defined azo BCs were obtained with controlled molecular weights and narrow polydispersities (Lehmann et al., 2000). 

Y. Li, F. Wang, J. Yang, D. Liu, A. Roy, S. Case, J. Lesko, and J. E. McGrath. Synthesis and characterization of controlled molecular weight di-sulfonated poly(arylene ether sulfone) copolymers and their applications to proton exchange membranes. Polymer, 47(11) 4210-4217, May 2006. 

Dubois, P., Jacobs, C., J6r5me, R., andTeyssii, P., 1991, Macromolecular engineering of Polylactones and Polylactides. 4. Machanism and Kinetics of Lactide Homopolymerization by Aluminium Isopropoxide. Macromolecules, 24 226634. Tromifoff, L., Aida, T., and Inoue, S., Formation of Poly(lactide) with controlled Molecular Weight. Polymerization of Lactide by Aluminum Porhyrin. 1987, Chem. Lett., 991 pp... 

Anionic polymerization is known to give model block copolymers with controlled molecular weights, narrow molecular weight distributions and versatile architecture. Anionic polymerization has been used for the synthesis of DHBCs in several eases although this type of polymerization teehnique is relatively intolerant to the presence of polar functionalities on the monomers utilized. A recent example has been described by Hadjichristidis and coworkers [6]. They have presented the synthesis of a series of poly (2-vinylpyridine-b-... 

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