Cyclic polymers: Synthetic strategies and physical properties

Abstract

Syntheses of cyclic polymers including cyclic homopolymers, cyclic block copolymers, sun-shaped polymers, and tadpole polymers are discussed on the basis of a differentiation between synthetic methods and synthetic strategies (e.g., polycondensation, ring-ring equilibration, or ring-expansion polymerization). Furthermore, all synthetic methods are classified as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed.

Synthesis of Amphiphilic Tadpole-Shaped Linear-Cyclic Diblock Copolymers via Ring-Opening Polymerization Directly Initiating from Cyclic Precursors and Their Application as Drug Nanocarriers

“…[1][2][3] It has been well-established that the topological structures and chemical composition of nonlinearshaped block copolymers can exhibit dramatic effects on the solution properties and self-assembling morphologies as compared with their linear counterpart. [4][5][6][7][8][9] It is worthy of noting that the developments of a variety of controlled radical polymerization techniques 10 such as atom transfer radical polymerization (ATRP), [11][12][13] reversible addition-fragmentation chain transfer (RAFT) polymerization, [14][15][16] and nitroxide-mediated polymerization (NMP) 17,18 have facilitated the synthesis of nonlinear-shaped polymers with varying chain architectures such as cyclic, 8,9,[19][20][21][22][23] (miktoarm) star, [24][25][26] star block copolymers, 27,28 comb, [29][30][31][32] sun-shaped, [33][34][35] H-shaped, [36][37][38] and θ-shaped 39,40 polymers. Among these nonlinear chain topologies, tadpole-shaped linearcyclic diblock copolymers [41]…”

Polyethylene‐Based Tadpole Copolymers

“…[40] Two samples with different molecular weights were synthesized ( Table 1). As shown in Figure S2 (Supporting Information), a slight shift of the elution peak of star polymer (PE-OH) 2 -(PS-Br) to the lower molecular weight side, as compared to the linear PE macroinitiator (PE-OH) 2 -Br, was observed which can be attributed to the www.advancedsciencenews.com smaller hydrodynamic radius of the corresponding threearm star polymer. [43] Then, the cyclization of the two PE arms, after transforming the OH to alkyne groups by esterification with propiolic acid, of the 3-miktoarm star by Glaser coupling reaction was performed leading to the tadpole-shaped copolymers with a ring PE head and a linear PS tail.…”

“…The polyethylene-based tadpole copolymer (c-PE)-b-PS was obtained according to the synthetics steps presented in Scheme 1. α,ω-Dihydroxy-polyethylene with 2-bromo-2-methylpropanoate group at the middle of the chain, (PE-OH) 2 -Br ( 1 H NMR, see Figure S1, Supporting Information) was synthesized by cyclic hydroboration and polyhomologation of the dimethylsulfoxonium methylide with 1,4-pentadiene-3-yl-2-bromo-2-methylpropanoate 1 as initiator, followed by ATRP of styrene to afford (PE-OH) 2 b-PS. [40] Two samples with different molecular weights were synthesized ( Table 1).…”

“…The heterofunctional initiator (polyhomologation and ATRP), the ATRP macroinitiator (PE-OH) 2 -Br, and the OH-functionalized 3-miktoarm star copolymers (PE-OH) 2 -b-PS, precursors of the tadpole copolymers, were synthesized following procedures described in a previous paper. [40] Details of the syntheses are given in the Supporting Information.…”

“…[1][2][3][4][5][6][7] To date, cyclic polymers with different structures such as diblock, [8] triblock terpolymer, [9] eight-shaped, [10] and tadpole copolymers [11][12][13][14][15] have been synthesized either by end-to-end linking or ring-expansion process. [16][17][18][19][20] Among them, tadpole homo/copolymers consisting of a ring polymer as a head and one linear polymer as a tail, are very interesting for rheology and self-assembly studies, since they combine two topologies in the same molecule.…”