Poly sequential polymerization

In poly(AAm-co-BMA)/PAAc IPNs (BMA is butyl methacrylate), the synthetic procedure applied was the sequential polymerization technique shown in Fig. 10. A monomer or set of comonomers is polymerized into a polymer gel. A second monomer is introduced and subsequently polymerized and crosslinked within the initial gel (AAm-co-BMA) matrix to form the IPN. 

Ma et al.177 synthesized a,co-dilithium poly(styrene-b-butadiene-b-styrene)s (PS-b-PBd-b-PS) by using l,3-bis(l-phenylethylenyl)benzene activated with 2 mol of s-BuLi as initiator for the sequential polymerization of butadiene and styrene in the presence of s-BuOLi in benzene. The cyclization reaction was performed under high dilution in cyclohexane with either dichlorodimethylsilane or MDPPE (Scheme 87). The cyclic copolymer was isolated by fractional precipitation. The only indication of the formation of this architecture was the lower intrinsic viscosity. 

Moreover, the reactivation of a cobalt-terminated polymer in the presence of second monomer leads to block copolymerization. In this respect, CMRP has aheady contributed to the preparation of the valuable copolymers listed in Table 4.1. For example, well-defined poly(acrylate) block copolymers were prepared via a sequential polymerization of acrylic monomers with cobalt porphyrin la or cobaloximes 2 [14, 20]. The synthesis of well-defined poly (acrylate)-b-poly(VAc) block copolymers was also achieved with complex la [26]. Co(acac)2 (3a see Figure 4.1) is the most prolific complex for the preparation of block copolymers, until now. Indeed, the sequential CMRP of VAc with NVP [33], AN [48], or vinyl pivalate (VPi) [49] leads to the corresponding block copolymers, in controlled fashion. Throughout the polymerization, the experimental conditions were necessarily adjusted, taking into consideration the reactivity of the second monomer. As an illustration of this, well-defined PVAc-b-poly(acrylonitrile) (PAN) copolymers could only be prepared via a bulk polymerization of VAc at 30 °C, followed by the AN polymerization at 0°C in solution in DMF [48]. In this case, the DMF not only serves as the solvent but also binds the metal and adjusts its reactivity. As a rule, the PVAc sequences of these copolymers were hydrolyzed in order to provide poly(vinyl alcohol) (PVA)-containing derivatives, such as hydrosoluble PVA-b-poly... 

Block-Type Brushes by Sequential Polymerization The sequential hving polymerization of two macromonomers or a macromonomer with a conventional comonomer forms either block-block- or block-coil-type brush structures. For example, giant rod-coil amphiphilic block copolymer bmshes were prepared via a stepwise metallocene-catalyzed polymerization [58]. In the first step, a concentrated solution of methacryloyl end-functionalized PS macromonomer (DP = 18.3, MWD = 1.05) was polymerized by the organosamarium(iii) catalyst in THF. After PS macromonomer was completely consumed, the active center remained living, and tert-butyl methacrylate tert-butyl methacrylate (tBMA) as a comonomer was added to grow the second block. After termination by ethanol, the poly(tert-butyl methacrylate) (PtBMA) coil block was hydrolyzed into a hydrophihc block, poly(methacrylic acid) (PMAA). The final product consisted of a hydrophobic PS brush block and a hydrophihc PMAA coil. The hydrophilic PMAA coil collapsed in nonpolar solvents, which forced the block-coil CPBs to self-assembled into giant micelles with PMAA as the core component and the stiff PS brush block as the shell to stabihze the micelles. 

Polystyrene-b-poly(vinylpyridine) with a molar mass of lOOOOgmol" was synthesized by the lithium naphthalide-initiated sequential polymerization of styrene and 2-vinylpyridine, followed by end-to-end intramolecular coupling with l,4-bis(bromomethylbenzene) in THF. The block copolymer was finally purified by predpitation-extraction procedures. 

For the solvent process, the ethyl acetate by-product can be recovered, refined, and sold as an additional product. This somewhat offsets the cost of sequential polymerization, hydrolysis, acetalization, and solvent recovery unit operations in one manufacturing plant. Because of the low capital investment required to produce PVB with market poly(vinyl alcohol) however, most of the recent published literature has dealt with the aqueous process. 

Fully methacrylic triblocks, containing a central rubbery poly(alkyl acrylate) block and two peripheral hard poly(alkyl methacrylate) blocks, are potential substitutes for the traditional styrene-diene-based thermoplastic elastomers (TPEs), which have relatively low service temperatures. Fully methacrylic triblock copolymers are able to cover service temperatures due to the varying Tg from — 50 C (poly(isooctyl acrylate)) to 190 C (poly (isobornyl methacrylate) [210]. Poly(methyl methacrylate)-Z)-poly(n-butyl acrylate)-Z)-poly(methyl methacrylate) triblock copolymers, which are precursors for poly(methyl methacrylate)- -poly(alkyl acrylate)-Z)-poly(methyl methacrylate) via selective transalcoholysis, have been synthesized by a three-step sequential polymerization of MMA, ferf-butyl acrylate (t-BuA), and MMA in the presence of LiCl as stabilizing ligand [211,212]. Various diblock copolymers, such as poly(methyl methacrylate)-Z)-poly( -butyl acrylate) and poly(methyl methacrylate)-Z)-poly( -nonyl acrylate), have been synthesized... 

There are numerous reports in the literature describing the synthesis of low polydispersity PNIPAm (co)poly-mers via CRP methods. For example. Binder et al. [54] described the synthesis of telechelic PNIPAm using functional NMP initiators modified via azide-alkyne cycloadditions. Efficient block copolymerization of NIPAm with styrene was achieved via sequential polymerization initiated by a-hydrogen alkoxyamine [55]. A PNIPAm block was first prepared and then chain extended with styrene yielding amphiphilic diblock copolymers. Initial attempts to use ATRP to prepare PNIPAm resulted in polymers with broad polydisperisities [56], but this problem was circumvented by utilizing a more efficient ligand for the initiator complex [57]. 

It is noteworthy that polymers of practical interest that exhibit a globular shape and unsymmetrical faces of the Janus-type architecture, not easy to make by conventional methods [89, 90], can be prepared by sequential ring-opening metathesis copolymerization of two different norbomenyl macromonomers. To this end, sequential polymerization of co-norbomyl polystyrene and a-norbornyl-poly(ethylene oxide) macromonomers in the presence of the Schrock initiator Mo(NAr)(ChrBu)(OC(CH3)(CF3)2)2 produced poly[polystyrene xycarbonyl-norbornene)-b-poly(ethylene oxide) xymethylene-norbomene)] block copolymer (122) in high yield [88] [Eq. (54)]. 

The history of well-defined BCPs with polyphenylene segments is quite long, similar to polyacetylenes (Section 13.3.1). In 1988, Francois et al. synthesized poly(p-phenylene)(PPP)-b-PS rod-coil BCPs based on living anionic polymerization (Zhong and Francois, 1988). After the sequential polymerization of styrene and cyclohexadiene, the poly(cyclohexa-l,3-diene)-b-PS was synthesized and subsequently aromatized with p-chloranil to afford the desired PPP-b-PS. Although the aromatization was not complete, they discovered special nonequilibrium honeycomb structures in which monodisperse pores are arranged in a hexagonal array by... 

With dibutylzinc initiator and sequential polymerization, Bailey and France prepared block copolymers of ethylene oxide and epsilon-caprolactone and of propylene oxide and mixed methyl-epsilon-caprolactone (184). In these preparations, the poly(ethylene oxide) segments were formed first, followed by epsiloncaprolactone addition. 

The presence of DMAP is essential to control the polymerization process. In the absence of DMAP, the polydispersity index of the polymer formed increases to 1.3, and the gel permeation chromatography (GPC) profile gives a small new peak whose MW is twice that of the major product. The high stability of the propagation centers allows the isolation of poly(PA) having active propagation sites, which can sequentially polymerize different monomers to give precisely controlled block copolymers. 

Various amphiphilic block copolymers have been synthesized by sequential polymerizations of the protected forms of functional monomers, followed by deprotection [28,34-36]. One example is the synthesis of PMA-6-poly (acrylic acid) (PAA), as shown in Scheme 3.4. A diblock copolymer, PMA-6-poly (tert-butyl acrylate) (P/BA) was prepared by first polymerizing MA, followed by the growth of rBA from the PMA macroinitiator. This diblock was then treated in dichloromethane with anhydrous triflic acid (TFA) at room temperature. Selective cleavage of the iert-butyl ester group of P/BA block occurred to produce the amphiphilic block copolymer, PMA-b-PAA. 

The approach cannot ordinarily yield ABA copolymers because poly(oxyethylene)oxy anions are unable to activate most vinyl monomers for sequential polymerization. However, in the presence of a strong base complexed with crown ether or cryptate ligands, POE chains with NHCH2Ph or OH end groups become sufficiently nucleophilic to initiate the polymerization of methyl and t-butyl methacrylates giving triblock polymers with central POE segments. ... 

Sequential polymerization with site transformation Block copolymers in which the active sites are not compatible are usually prepared in two steps. First, a site transformation is performed, after which initiation of the ROP occurs. Block copolymers with a poly(styrene) or a poly(butadiene) block and a poly(carbonate) block, for instance, are obtained after site transformation of a carbanionic to an alcoholate species [25]. The initiation reaction of the ROP of DTC using living vinyl (or diene) polymers with alkali metal counterions as initiators, was performed after site transformation of the carbanionic into the alcoholate species... 

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