Chlorination termination

With respect to the initiation of cationic chain polymerizations, the reaction of chlorine-terminated azo compounds with various silver salts has been thoroughly studied. ACPC, a compound often used in condensation type reactions discussed previously, was reacted with Ag X , X, being BF4 [10,61] or SbFa [11,62]. This reaction resulted in two oxocarbenium cations, being very suitable initiating sites for cationic polymerization. Thus, poly(tetrahydrofuran) with Mn between 3 x 10 and 4 x lO containing exactly one central azo group per molecule was synthesized [62a]. Furthermore, N-... 

The first diblock copolymer brushes synthesized in our group were made by a combination of carbocationic polymerization and ATRP (Scheme 1) [46]. Zhao and co-workers [47] synthesized diblock copolymer brushes consisting of a tethered chlorine-terminated PS block, produced using carbocationic polymerization, on top of which was added a block of either PMMA, poly(methyl acrylate) (PMA) or poly((Ar,M -dimethylamino)ethyl methacrylate) (PDMAEMA), synthesized using ATRP. The thickness of the outer poly(meth)acrylate block was controlled by adding varying amounts of free initiator to the ATRP media. It has been reported that the addition of free initiator is required to provide a sufficiently high concentration of deactivator, which is necessary for controlled polymerizations from the sur-... 

Copolymers. Copolymers from mixtures of different bisphenols or from mixtures of dichlorosulfone and dichlorobenzophenone have been reported in the patent literature. Bifunctional hydroxyl-terminated polyethersulfone oligomers are prepared readily by the polyetherification reaction simply by providing a suitable excess of the bisphenol. Block copolymers are obtained by reaction of the oligomers with other polymers having end groups capable of reacting with the phenol. Multiblock copolymers of BPA-polysulfone with polysiloxane have been made in this way by reaction with dimethyl amino-terminated polydimethylsiloxane the products are effective impact modifiers for the polyethersulfone (79). Block copolymers with nylon-6 are obtained when chlorine-terminated oligomers, which are prepared by polyetherification with excess dihalosulfone, are used as initiators for polymerization of caprolactam (80). 

Silylating agents have also been used to treat glassware before handling moisture-sensitive compounds. For example, a chlorine-terminated polydimethyl si-loxane is available commercially.3 These reagents suppress the basicity of the glass and provide a hydrophobic surface. 

The copolymer (Me2SiPh2GeMe2Si) (7) had a molecular weight of Mw = 1.1 x 103 (Mw/Mn = 1.31) and was isolated in 25% yield. The authors claim that the polymerizabil-ity of a,electrochemical conditions is mainly affected by the substituents at the chlorinated terminal silicon atoms, which provides interesting options for the design of copolymers with ordered sequences of silicon and germanium atoms. 

Before the development of living cationic polymerization in the 1980s, Kennedy and his co-workers devised another way to synthesize end-functionalized polymers, which uses special reagents called inifer, or initiator-chain transfer agents [129]. The method is primarily for the synthesis of polyisobutene with a tertiary chlorine terminal, which is, however, a synthon for a variety of other functional groups. These developments have been reviewed extensively [1,3,130] and fall outside the scope of this chapter. 

Several studies of the mechanism of the sodium coupling reaction have been carried out, and a mechanistic model has emerged which accounts for most of the experimental observations. The reaction chain appears to be anionic in nature. The first step is believed to be the slow reaction of the dichlorosilane with sodium to give an anion (equation 34). The chain-extending process is the reaction of polymer silyl anions with dichlorosilane molecules (equation 35), followed by rapid reduction of the chlorine-terminated polymer to the anion (equation 36). Reduction must take place at the surface of a sodium particle. As polymerization occurs, some molecules may break free from the sodium surface once in solution away from the metal, chain extension would cease. This portion may give rise to the low-molecular weight polymer. Other molecules probably become entangled at the sodium surface and so cannot break free. They therefore continue to react with fresh dichlorosilane, and eventually... 

The synthesis of block copolymers from a chlorine-terminated pdiymer, Et2AlCl and a cationically sensitive moncmer was achieved by Kennedy and collaborators and apparently constitutes a strong indication for the validity of their initiation mechanism. The blocking of styrene on pdyisobutene with chlorine end poups and of isobutene on polystyrene with chlorine end poups was hi y efficient This is apparently in contradiction with air interpretation, because if we assume the occurrence of the exchange reaction... 

A bicyclic monomer containing a maleate ester unit (M-43) undergoes a very slow 2,6-addition polymerization with 1-12 (X = Cl)/CuCl/L-l in the bulk at 130 °C to afford narrow MWDs (Mw/Mn 1.2) (11% conversion in 2 weeks).223 Enchainment of this monomer to the chlorine-terminated polystyrene increases the decomposition temperature of the polymer. 

The polystyrene obtained by living cationic polymerization with R—Cl/Lewis acid possesses a carbon-chlorine terminal that is subsequently used for the living radical polymerizations of acrylates and methacrylates to give block copolymers such as B-65 to B-67 376-378... 

THF) of the chlorine-terminated products led to olefin telechelic derivatives which in turn yielded many potentially useful materials (14). Thus hydroboration (a quantitative reaction) gave rise to new polyisobutylene-based diols and triols which in combination with isocyanates gave unique polyurethanes ... 

Zhao and Brittain also used the grafting from technique to grow polymers off silicon surfaces [329]. In their example, however, they first prepared tethered pSt cationically, which was terminated with a chlorine chain end, then used it as the initiator for the ATRP of MMA using the CuBr/PMDETA catalyst system. Use of a chlorine-terminated pSt chain in conjunction with a CuBr catalyst, however, produces a mismatch between the rates of cross-propagation and the rate of po-... 

HM= = dead polymer formed by all types of chain transfer HM X = chlorine-terminated polymer (from HX)... 

PA-6-g-polyolefin or PA-6-g-PS. The resultant graft copolymer could be utilized to compatibilize PA blends with PO or styrenic polymers. Although this approach is relatively straightforward, commercialization had not occurred. Ahm et al. [1997] utilized a similar approach to compatibilize PA-6 and polyethersulfone (PES) PA-6-PES-PA-6 block copolymer were synthesized by anionic polymerization of s-caprolactam with chlorine terminated PES. 

Which determinative technique to use is dictated by the physical and chemical nature of the analyte of interest. The organics protocol flowchart introduced in Chapter 2 serves as a useful guide. Let us consider how we would determine which instrumental technique to use for the following example. Ethylene glycol, 1,2-ethanediol (EG), and 1,2-dichloroethane (1,2-DCA) consist of molecules that contain a two-carbon backbone with either a hydroxyl- or chlorine-terminal functional group. The molecular structures for these are as follows ... 

Under the tradename Copel LR Resin, silicone polycarbonates found applications ranging from oxygen enrichment membranes (including heart-lung machines), aerospace canopies and interlayers for bullet-proof glazing. They are prepared by the phosgenation of bisphenol A and chlorine terminated polydimethylsiloxane oligomer in methylene chloride with pyridine as a base acceptor (Eq. 7). 

In addition to THE, iso-butylene has also been used as another important cationic monomer in the synthesis of this particular block copolymer. The report by Kennedy et al. represents a typical example of this kind of transformation. First, t-chlorine-terminated PIB was prepared and converted into a... 

In addition, all bimolecular activation-controlled reactions are independent of the degree of polymerization [6]. Simple 8 2 reactions between reactive groups attached to chain ends of mono-disperse macromolecules in a wide range of molecular weights are independent of the DP [7, 8] in the range of 20-2,000 [7]. This was shown on three different reactions. In the first one, the reactivities of chlorine-terminated low and high molecular weight polystyrenes towards polystyryllithium are equal in benzene and cyclohexane solvents ... 

For instance, a chlorine-terminated fully aromatic sulfone, 4,4 -dichlorodiphenylsulfone (DCDPS) was reacted [84] with two aromatic diols, namely dihydroxy-diphenylsulfone (DHDPS) and hydroquinone (HQ). The reaction product was RLS80, a chlorine-ended copolyethersulfone with ESES units -( )-S02-( )-0-( )-S02-( )-0- and EES units -c )-S02-( )-0-( )-0-, where ( ) is a phenyl ( = Q ). Figure 45.22 contains the MALDI spectrum of RLS80 along with an expansion of the 3.65-4.44 kDa region. The spectrum shows more than 130 well-resolved peaks, ranging from 1.0 to 9.0 kDa. The most intense peaks are due to chains B and B, where... 

In an extensive work on polysiloxane polymer liquid crystals, Finkelmann et al. examined their performance in a twisted nematic electro-optical cell. In parallel with the polymer measurements, analogous studies were carried out on low molar mass nematic compounds of equivalent dielectric anisotropy (Ae). Both the low molar mass nematic materials and the polymer side-group moieties were mixtures of methoxy- (or alkyloxy-) and chlorine-terminated benzoate esters. Cells were prepared using rubbed polyimides and in the polymer case the samples were annealed for several hours to obtain defect-free aligned textures. Measurement of the threshold voltages, for both the low molar mass compounds and the polymer, showed ... 

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