Living Nature Of Polymerization Research Articles

Multicyclic Polymer Synthesis through Controlled/Living Cyclopolymerization of α,ω-Dinorbornenyl-Functionalized Macromonomers

A novel synthesis of multicyclic polymers that feature ultradense arrays of cyclic polymer units has been developed by exploiting the cyclopolymerization of α,ω-norbornenyl end-functionalized macromonomers mediated by the Grubbs third-generation catalyst (G3). Owing to the living polymerization nature, the number of cyclic repeating units in these multicyclic polymers was controlled to be between 1 and approximately 70 by varying the initial macromonomer-to-G3 ratio. The ring size was also tuned by choosing the molecular weight of the macromonomer; in this way we successfully prepared multicyclic polymers that possess cyclic repeating units composed of up to about 500 atoms, which by far exceeds those prepared to date by cyclopolymerization. Specifically, cyclopolymerizations of α,ω-norbornenyl end-functionalized poly(l-lactide)s (PLLAs) proceeded homogeneously under highly dilute conditions (∼0.1 mM in CH2Cl2) to give multicyclic polymers that feature cyclic PLLA repeating units on the polynorbornene bac...

A Single-Site Iron(III)-Salan Catalyst for Converting COS to Sulfur-Containing Polymers.

An iron(III) complex of tetradentate N,N′-disubstituted bis(aminophenoxide) (designated as salan, a saturated version of the corresponding salen ligand) with a sterically hindered organic base anchored on the ligand framework, can selectively mediate the conversion of carbonyl sulfide to sulfur-containing polymers by the copolymerization with epoxides. This single-site catalyst exhibits broad substrate scope, and the resultant copolymers have completely alternating structures. In addition, this catalyst is efficient in producing diblock copolymers, suggesting a living polymerization nature.

Tandem Metal-Coordination Copolymerization and Organocatalytic Ring-Opening Polymerization via Water To Synthesize Diblock Copolymers of Styrene Oxide/CO2 and Lactide

Selective transformation of carbon dioxide and epoxides into degradable polycarbonates (CO(2)-based copolymer) has been regarded as a most promising green polymerization process. Although tremendous progress has been made during the past decade, very few successful examples have been reported to synthesize well-defined block copolymers to expand the scope of these green copolymers. Herein, we report a tandem strategy combining two living polymerization techniques, salenCo(III)X-catalyzed styrene oxide SO/CO(2) copolymerization and ring-opening polymerization of lactide with DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), for the synthesis of poly(styrene carbonate-block-lactide) copolymers. The key to the success of this tandem strategy is the judicious choice of water as the chain transfer and/or chain terminator reagent, which is added at the end of the salenCo(III)X-catalyzed SO/CO(2) copolymerization to in situ generate hydroxyl groups at the end of the polymer chains. The resulting polycarbonates with -OH end groups can thus be directly used as macroinitiators to subsequently initiate ring-opening polymerization of lactide to synthesize the diblock copolymers. Because of the living polymerization nature of both steps in this tandem strategy, we have demonstrated that the diblock copolymers synthesized possess well-defined structures with narrow molecular weight distributions and controllable lengths of both styrene carbonate and lactide blocks.

Chain‐Growth Polycondensation: Living Polymerization Nature in Polycondensation and Approach to Condensation Polymer Architecture

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Chain-Growth Polycondensation: Living Polymerization Nature in Polycondensation and Approach to Condensation Polymer Architecture

In this review article, polycondensation that proceeds in a chain-growth polymerization manner (“chain-growth polycondensation”) for well-defined condensation polymers are described. Our approach to chain-growth polycondensation is (1) activation of polymer end group by substituent effects changed between monomer and polymer and (2) phase-transfer polymerization in biphase composed of monomer store phase and polymerization phase. In the approach (1), a variety of condensation polymers such as aromatic polyamides, aromatic polyesters, aromatic polyethers, poly(ether sulfone), and polythiophene with defined molecular weights and low polydispersities were obtained. Their polycondensations had all of the characteristics of living polymerization: a linear correlation between molecular weights and monomer conversion maintaining low polydispersities, and control over molecular weights by the feed ratio of monomer to initiator. Taking advantage of the nature of living polymerization in this polycondensation, we synthesized diblock copolymers of different kinds of aromatic polyamides and of aromatic polyamide and conventional polymers such as poly(ethylene glycol), polystyrene, and poly(tetrahydrofuran), as well as triblock copolymers and star polymers containing aromatic polyamide units. Some copolymers were arranged in a supramolecular self-assembly. In the approach (2), the polycondensation of solid monomer dispersed in organic solvent with a phase transfer catalyst (PTC) was carried out, where solid monomer did not react with each other, and the monomer transferred to organic solvent with PTC reacted with an initiator and the polymer end group selectively in organic solvent, to yield well-defined polyesters.

Chain-Growth Polycondensation for Aromatic Polyethers with Low Polydispersities: Living Polymerization Nature in Polycondensation

Polycondensation normally proceeds in a step-growth reaction manner to give polymers with a wide range of molecular weights. However, the polycondensation of potassium 5-cyano-4-fluoro-2-propylphenolate (1) proceeded at 150 °C in a chain polymerization manner from an initiator, 4-fluoro-4‘-trifluoromethylbenzophenone (2a), to give aromatic polyethers having controlled molecular weights and low polydispersities (Mw/Mn ≤ 1.1). The resulting polycondensation of 1 had all of the characteristics of living polymerization and displayed a linear correlation between molecular weight and monomer conversion, maintaining low polydispersities. The MALDI−TOF mass spectrum of poly1 revealed that this polycondensation did not include conventional step-growth polycondensation which gave the polymer without initiation unit and macrocycles. The poly1 with low polydispersity showed higher crystallinity than that with broad molecular weight distribution, obtained by the conventional polycondensation of 1 without 2a.

“LIVING”POLYMERIZATION OF BUTADIENE BY RARE EARTH COORDINATION CATALYST

In this paper, the kinetic method was used to study the polymerization of butadiene initiated by NdCl 3 ·3i-PrOH-AlEt 3 catalyst system, at-70, -30 and 0℃. Results obtained indicated that there are no both reactions of detectable transfer limiting molecular weight of polymers and irreversible termination with deactivation of propagation centers. It was found that polymers produced had narrow molecular weight distributions (MWD) and extremely high cis-1,4 content, and that the living chain had a very long lifetime. Block copolymers of butadiene and isoprene were prepared and characterized by means of GPC, 13 C NMR, and IR. It was fully proved that the polymerization of butadiene initiated by the rare earth catalyst under these conditions had a living polymerization nature.