Block copolymers PTBA triblock

Liu and coworkers have investigated PI-PCEMA-PtBA triblock copolymers in which the central PCEMA block was cross-linked by UV irradi-... 

For nanofibers and nanotubes, backbone modification refers to selective chemical transformation of one or more of the core blocks. In our preparation of nanotubes from the PI-PCEMA-PtBA and PS-PCEMA-PtBA triblock nanofibers, the core PI and PtBA blocks were sculpted away either fully or partially. These reactions are examples of nanofiber backbone modification. One can also consider inorganic reactions carried out inside one of the block copolymer phases to be a kind of backbone modification. These reactions lead to the formation of interesting polymer-inorganic hybrid nanostructures. This topic will be reviewed in the following paragraphs. 

A remarkable example reported by Huang indicates versatility of the transformation approaches in block copolymer synthesis. In his recent work, an ABC triblock terpolymer (PSt-Z -PEO-l7-PtBA) was prepared by a combination of three... 

The concept was further extended to the preparation of PtBA-l7-PIB-l7-PSt (ABC) triblock and amphiphilic penta-block copolymers based on PIB. ° ... 

RAFT-CTAs can be prepared in a similar way and thus combined with ROMP for the synthesis of well-defined block copolymers. ABA-type triblock polymers of 1,5-cyclooctadiene (by ROMP) and St or tBA (by RAFT) were synthesized by Mahanthappa et In the first step of the process, the synthesis of telechelic PBs possessing trithiocarbonate-functionalized termini was performed using the specially designed difanctional CTA containing double bond in the middle. The RAFT polymerizations of conventional monomers mediated by the telechelic polymers gave rise to PSt-b-PB-l7-PSt and PtBA-l -PB-l7-PtBA (Scheme 68). 

Block copolymers comprised of flexible poly(n-butyl acrylate) or PtBA and rigid P3HT segments have been synthesized by ATRP and by oxidative polymerization (31). Two synthetic routes were followed starting from either the flexible coil for the rod-coil diblock copolymers or the rod P3HT segment for the coil-rod-coil triblock copolymers. ... 

The preparation procedure of narrowly distributed Seesaw-type macromonomer triblock copolymers, poly(tert-butyl acrylate)-polystyrene-poly(terr-butyl acrylate) (PtBA-PS-PtBA), with one alkyne group in the center of the PS block and one azide group at the end of each PtBA block is similar to that of macromonomer polystyrene homopolymers. The schematic synthesis of PtBA-PS-PtBA triblock copolymer is shown in Fig. 3.8. The corresponding DP values were calculated from area ratio of corresponding peaks in NMR spectrum, as shown in Fig. 3.9, and the molecular parameters of our obtained triblock copolymers macromonomer PiBA-PS-PtBA with different St and tBA molar contents and molar masses are summarized in Table 3.2. 

The nanopartide S3mthesis process can be further modified through the use of additives during assembly. These additives vary from homopolymer of one of the block segments to surfactants and even metal oxides. Liu et al. demonstrated the assembly of a triblock copolymer of PS-b-PCEMA-b-PtBA in the presence of PS homopolymer.Adjustment of the volume fractions of the different blocks was achieved through modification of the triblock composition and the ratio of triblock and PS homopolymer and resulted in the formation of cylinders comprising a PtBA core surrounded by a PCEMA layer in a matrix of PS. The triblock and homopolymer mixture was cast from toluene the solvent was then allowed to evaporate slowly and the film was annealed. The nanocylinders were stabilized... 

While the original paper (Dou et al., 2010) reported the study of several pairs of diblock and triblock copolymers, we will briefly discuss, in this section, results obtained from two pairs of PMMA-fc-PNH2-h-PMMA and PtBA-(j-PSCOOH samples (Figure 24.14). Here, PNH2 can be either PGNH2 or PHNH2. The repeat unit number, n, for each of the PMMA blocks of the PMMA-fc-PNH2-f -PMMA samples was 285 and that for the middle block. 

As the order of monomer addition is less important in TERP compared to that in other LRP methods, it was possible to prepare ABA- and ABC-triblock copolymers starting from diblock macro CTAs (Scheme 17). Treatment of PMMA-b/ocfe-PSt and PMMA-b/ocfe-PtBA macro CTAs with MMA gave the desired ABA-triblock copolymers with narrow MWDs. ABC-triblock copolymers with different monomer sequences of St, MMA, and tBA, namely, PSt-block-PKibAA-block-PtBA, VisAMA-block-PSt-block-VBA, and PbAMA-block-PtBA-block-PSt, were also synthesized in a controlled manner by the successive addition of each monomer. These triblock copolymers were all obtained in a highly controlled manner with narrow MWDs. 

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