Cyclic polymer synthesis

Shin EJ, Jeong W, Brown HA, Koo BJ, Hedrick JL, Waymouth RM (2011) Crystallization of cyclic polymers synthesis and crystallization behavior of high molecular weight cyclic poly (epsilon-caprolactone)s. Macromolecules 44 2773-2779... 

While the PDIs of the REMP macrocycles are higher than those typically reported for the ring-closure approach, the molecular weights obtained are by far the highest reported to date for a cyclic polymer synthesis. The catalyst design optimization has yielded improved polymerization catalysts, and promises to broaden the versatility of this route. For example, by using a dendronized monomer, Grubbs and coworkers have demonstrated the synthesis of dendronized cycHc polymers and confirmed their cyclic structure with AFM [59], and have also synthesized cycHc polymers with threaded rotaxanes [60]. 

Since one of the substrates is a cyclic alkene there is now the possibility of ring-opening metathesis polymerisation (ROMP) occurring which would result in the formation of polymeric products 34 (n >1). Since polymer synthesis is outside the scope of this review, only alkene cross-metathesis reactions resulting in the formation of monomeric cross-coupled products (for example 30) will be discussed here. 

The catalyst Cl2Ru(PCy3)2(=CHCH=CPh2), c.f., Figure 1.8, is obtained in a yield of 88%. In the same way, catalysts, where the metal atom is in a ring, can be synthesized. This type of catalysts is suitable for the synthesis of cyclic polymers (26). The synthesis route is shown in Figure 1.9. 

The ruthenium catalyst can be used to catalyze the synthesis of a cyclic poly(octenamer). The catalyst is added to ris-cyclooctene in CH2CI2 solution at 45° C. The intermediate macrocyclic complex undergoes an intramolecular chain transfer to yield the cyclic polymer and regenerate the catalyst. 

The emphasis in the approaches to boron nitride [10043-11 -5], BN, precursors has been concentrated on cyclic compounds. There have been recent reports of trimethylsilyl-substituted aminoboranes being evaluated as B—N precursors. These are linear borylamines containing up to four boron atoms. Compounds were also synthesized with free —NH2 groups amenable to condensation with either dihaloboranes or dihaloborazines (65) and offering suitable monomers for linear B—N polymer synthesis and borazine-ring-linking applications. 

Synthesis of Cyclic Polymers Using Addition Polymerization. 126... 

Synthesis of Cyclic Polymers by Ring-Opening Polymerizations. 154... 

Abstract Thousands of polymeric materials have been made into synthetic polymers, based on a linear structure, and used in commercial applications. The study of synthetic polymeric materials has focused on those derived from long chain linear molecules. Alternatively, cyclic polymers (also referred to as polymer rings or macrocycles) can be prepared, which not only can be branched or cross-linked, but can also form nonco-valently linked structures based on their loop topology. Through a number of different approaches and advances in cyclization techniques, a wide range of novel cyclic polymers have been synthesized in good yields. This review will focus on a variety of synthetic methods and some properties of cyclic polymers using many polymerization mechanisms in various fields of polymer synthesis. 

Fig. 5 Synthesis of cyclic polymer using polymerization of styrene with cyclic initiator...

A cyclic polymer of methyl methacrylate was also synthesized using a het-erotelechelic polymer precursor, although the formation of living polymer of methyl methacrylate is more difficult than that of styrene. Mizawa et al. described the synthesis of heterotelechelic poly(methyl methacrylate) containing a-maleimide-tw-dienyl end groups and its intramolecular cyclization... 

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