In-situ anionic polymerization

Butadiene-isoprene copolymer (BIR)/clay nanocomposites too have been prepared through anionic in-situ polymerization by Zhang et al. in the presence of polar additives such as N,N,N, N -tetramethylethanediamine (TMEDA) [24]. The composites were prepared as follows a certain amount of butadiene, isoprene (butadiene/isoprene = 1/lwt/wt), TMEDA, OC-toluene mixture was introduced into a 250ml reactor and stirred for 3 h. Then, a small amount of -BuLi was added as impurities scavenger, before introducing the stoichiometric amount of initiator (TMEDA/n-BuIi = 0.2) to start the polymerization. The reaction was performed at two different polymerization temperature (30°C and 60°C) for 6h. TMEDA polar molecules were found to have a rather strong effect on the copolymer 

In another paper, as already observed by Zhang et al. [25], liao demonstrated that the experiments carried out with a toluene- or xylene-OC suspension instead of a cyclohexane one, resulted in the formation of more stable emulsions, so that aromatic solvents could be successfully used to synthesize PB/day nanocomposites by in-situ polymerization through the anionic route [22], 

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Viscoelastic properties of elastomer-based CPNCs were measured at a constant frequency of 1 Hz as a temperature sweep of the dynamic moduli. Exfoliated CPNCs with polybutadiene (PBD) or polyisoprene (IR) matrix were prepared by in situ anionic polymerization, with Tg increasing by about 10°C upon incorporation of 6.2 wt% organoclay [Liao et al 2005,2006]. However, contrary to expectations, these CPNCs did not show improved dynamic tensile storage modulus, E. ... 

A remarkable special property of nitrate esters is the ability to catalyze some additional polymerization reactions [42]. In nitroglycerine, both styrene and methyl methacrylate can be self-polymerized. If the amount of nitroglycerine is up to 5-20 portion (weight fraction), equals to 10 % of polymers, the polymerization rate will be fastened. The molecular weight of polymers is less than that obtained through slowly polymerization or in situ anionic polymerization. 

Billups and co-workers prepared PMMA-grafted SWCNTs by in situ anionic polymerization in the presence of debundled nanotube salts serving as... 

Gong Y, Liu A and Yang G (2010) Polyamide single polymer composites prepared via in situ anionic polymerization of e-caprolactam. Compos Part A 41 1006-1011. 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

Finally, Yan et cd. [66] utilized the in-situ anionic ring-opening polymerization to prepare monomer casting PA 6-MWNTs nanocomposites. The typical functionalization process of MWNTs by COOH groups was not therein applied, as the... 

The following paragraphs highlight the work concerning the synthesis of 1,3-butadiene based PCNs by in-situ, anionic and spereospedfic, polymerization. 

In order to obtain a good combination of end properties, numerous copolymers with a variety of nonpolyamide blocks have been prepared using polymeric activators and accomplishing the in situ anionic lartam potymerization. The main... 

Protonic initiation is also the end result of a large number of other initiating systems. Strong acids are generated in situ by a variety of different chemistries (6). These include initiation by carbenium ions, eg, trityl or diazonium salts (151) by an electric current in the presence of a quartenary ammonium salt (152) by halonium, triaryl sulfonium, and triaryl selenonium salts with uv irradiation (153—155) by mercuric perchlorate, nitrosyl hexafluorophosphate, or nitryl hexafluorophosphate (156) and by interaction of free radicals with certain metal salts (157). Reports of "new" initiating systems are often the result of such secondary reactions. Other reports suggest standard polymerization processes with perhaps novel anions. These latter include (Tf)4Al (158) heteropoly acids, eg, tungstophosphate anion (159,160) transition-metal-based systems, eg, Pt (161) or rare earths (162) and numerous systems based on tri flic acid (158,163—166). Coordination polymerization of THF may be in a different class (167). 

Proliferous Polymerization. Eady attempts to polymerize VP anionicaHy resulted in proliferous or "popcorn" polymerization (48). This was found to be a special form of free-radical addition polymerization, and not an example of anionic polymerization, as originally thought. VP contains a relatively acidic proton alpha to the pyrroHdinone carbonyl. In the presence of strong base such as sodium hydroxide, VP forms cross-linkers in situ probably by the following mechanism ... 

S-Methacryloyloxy-ljl -biadamantane, MBA, (Scheme 4) was efficiently polymerized anionically using [ l,l-bis(4/-trimethylsilylphenyl)-3-methylpen-lyl]lithium as the initiator, prepared in situ by the reaction of s-BuLi with l,l-bis(4-trimethylsilylphenyl)ethylene [17]. The polymerization took place at - 50 °C in order to avoid the solubility problems of the monomer, observed at - 78 °C. Narrow molecular weight distribution block copolymers of rather low molecular weights of PMBA with fBuMA and (2,2-dimethyl-... 

Superoxide anion formed in situ in a solution exposed to air (i.e. with only a small concentration of O2) has been used as an EGB to generate nitroalkane anions that may add to activated alkenes or to carbonyl compounds [130, 131]. An example is shown in Scheme 33. The reaction is catalytic since the product anion can act as a base toward the nitroalkane. Using the nitroalkane as the solvent favors the proton transfer pathway over the competing addition of the product anion to a second molecule of activated alkene, a pathway that may lead to polymerization [130]. In some cases, better yields of the Michael addition product were obtained if a stoichiometric amount of the anion was formed ex situ (with O2 as the PB), and the activated alkene added subsequently ]130, 132]. 

Atmospheric oxygen may initiate in situ polymerization [55] as well as hght as exemplified by the photo-induced isomerization/polymerization of (Z,Z)-muconate anions in the gallery space of LizAl LDH [61] and the photoisomerization of indolinespirobenzopyran [62]. 

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