Poly , ’’living synthesis procedure

The direct synthesis of a diblock copolymer of styrene and THF has been achieved by coupling polystyryl-lithium with living cationic poly THF. Analogous procedures have led to the preparation of ABA and (AB)n multiblock copolymers. 

Ion coupling of anionic and cationic living polymers is an interesting procedure for the synthesis of a well-defined block copolymer. Attempted coupling of the polystyrene anion with the poly-THF cation initiated by triethyloxonium tetrafluoro-borate yielded a block copolymer mixed with homopolymers394. The block ef-... 

Killian et al. [21] described the well-performing a-diimine-based catalysts after the development of a procedure for the living polymerization of a-olefins based on Ni a-diimine catalysts and application of this procedure to the synthesis of diblock and triblock poly(a-olefins) (Scheme 3.11). Moreover, they found that the ratio of 1,2—versus 2,1-insertion is sensitive to the nature of the a-diimine ligand [21]. 

The synthesis of a well defined block copolymer, containing a poly(N-vinylimidazole) block (PVim), has been demonstrated by Ge et al. [23]. The polymerization was realized via a RAFT procedure employing xanthates as chain transfer agents. Initially, the polymerization of NIPAM monomer, affording PNIPAM macro-CTA, was realized followed by the polymerization of Vim, Figure 4. The obtained block copolymers had controllable molecular characteristics with a Mw/M value ca. 1.2. The living nature of the Vim polymerization has been confirmed by kinetic experiments, for the first 150 min of the polymerization reaction. It has to be noted that the above procedure was the first example of the synthesis of PVim containing block copolymers. 

Poly(iV-alllinear poly(isopropylenimine) (PiPI) back in 1974 based on the hydrolysis of poly(2,5-dimethyl-2-oxazoline), prepared by living CROP of the corresponding 2-oxazoline monomer. The PiPI is of interest as it is the simplest PAI with a chiral main-chain structure. Even though this specific example yielded a racemic PiPI, this synthetic procedure also provides access to a PiPI with controlled stereochemistry if... 

Despite a number of investigations, the efficient synthesis of co-epoxide-functionalized polymers in hydrocarbon solution with lithium as counterion at room temperature had not been reported. Takenaka et developed an efficient synthesis of epoxide-functionalized polystyrenes and poly-isoprenes by terminating the corresponding living polymeric anions with (2-bromoethyl)oxirane at -78 °C in THE as shown in eqn [27]. Termination of either PSLi or PlLi by inverse addition to 2-3 equivalents of (2-bro-moethyl)oxirane reportedly produced the corresponding epoxy-functionalized polymers in quantitative yields as determined by NMR and TLC-FID chromatography. However, the requirements of -78 °C and THF as solvent limit the usefulness of this procedure. 

Two-step procedures have sometimes been found more suitable for the synthesis of macromonomers. With poly(ethylene oxide) or poly(caprolactone), for instance, the living polymer has been protonated and reacted thereafter with protected esters or amines, fitted with a polymerizable unsaturation (Scheme 28). High yields can be attained, and no side reactions have been observed. 

---