Polymerization of Cycloalkanes

Control of End Groups in Anionic Polymerizations Using Phosphazene Bases and Protic Precursors As Initiating System (XH-ButP4 Approach): Application to the Ring-Opening Polymerization of Cyclopropane-1,1-Dicarboxylates

“…Polymerizations of electrophilic cyclopropanes such as 1 are typically initiated by soft nucleophiles such as cyanide or thiolate anions . Several reports have already established that thiophenolates PhSM (with M = Li, Na, K, or tetraalkylammonium (R 4 N)) are particularly convenient as initiators in the polymerization of 1 , yielding full conversion of the ring-opened adduct, with higher initiation rate constants than those observed for the propagation step and without side reactions. ,, In a recent report, we established that the Bu t P 4 /PhSH couple generated an excellent initiator in situ, requiring lower reaction temperatures for the initiation step than those typically needed with alkali metal thiophenolates ( k p = 5.8 × 10 −4 L·mol −1 ·s −1 in THF at 60 °C for the Bu t P 4 /PhSH initiator vs k p = 2.0 × 10 −4 L·mol −1 ·s −1 in DMSO at 130 °C for a sodium thiophenolate initiator (Figure S1 in the Supporting Information)) .…”

“…Polymers with very narrow polydispersities ( M w / M n < 1.08) could be obtained according to a living process. Moreover, satisfying polymerization rates were obtained under mild conditions ( k p = 5.8 × 10 −4 L·mol −1 ·s −1 in THF at 60 °C) compared to the conventional route, which uses alkali metal thiophenolates as initiators. − Propagation in this reaction occurs via malonate carbanions …”

Pd-Catalyzed Ring-Opening Polymerization of Cyclobutanols through C(sp3)–C(sp3) Bond Cleavage

“…The polymerization processes based on the opening of cyclic monomers (ring-opening polymerization, ROP) have been deeply studied during the last years − and keep on being at the forefront of the materials science research arena. − Two different types of ROP methodologies can be distinguished: (a) those based on the cleavage of C–heteroatom bonds and (b) those in which C–C or CC bonds of cyclic monomers are split. In the first case, these processes commonly rely on the use of heterocyclic rings, such as lactides, carbonates, or epoxides, in which a C–O bond is broken (Scheme a). ,, Within the second group, the most studied processes deal with the use of cyclic alkenes, such as norbornene, in which the CC bond undergoes a metathesis reaction (known as ROMP) (Scheme a). , The possibility to harness the cleavage of single carbon–carbon bonds of molecular skeletons offers huge opportunities to develop new synthetic routes, given the ubiquitous presence of such chemical linkages in organic compounds. − However, the availability of ROP methods that make use of the cleavage of C­(sp 3 )–C­(sp 3 ) bonds is much more restricted compared to those based on the C–heteroatom or CC bond cleavage . These methodologies are based on the use of strained carbocycles, which can be polymerized through radical, anionic, or cationic mechanisms (Scheme b).…”

Design of Optimized Reaction Conditions for the Efficient Living Anionic Polymerization of Cyclopropane‐1,1‐Dicarboxylates

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The ringopening polymeri zation of cyclopropanes was not a new concept at the time we started investigating the issue, but previous attempts had always led to oligomers, with broad to very broad molecular weight dis tributions. [14] For the first time, with the advent of our activated monomer approach, efficient procedures to polymerize livingly threemembered ring carbon monomers became available, yielding carbonchain polymers substituted on every third atom alongside the backbone (see Scheme 1A for an example). The living character of the anionic polymerizations enabled us to control molecular weights and usually obtain very low polydis persity indexes (M w /M n < 1.05).…”

“…In addition, high temperatures, up to 120-140 °C, can be used and further modi fications of the obtained macrocarbanion with electrophiles are possible due to the excellent thermal stability and wellknown nucleophilicity of malonate carbanions, the propagating species involved in these polymerizations. [3,7,14] The prototypical monomers that have been efficiently polymerized thus far in this series of activated cyclopropanes are based on cyclopropyl rings 1 geminally substituted by two electronwithdrawing groups, typically esters (Scheme 1) but also nitriles. Monomers with two propyl ester groups (either as n or ipropyl) have been particularly investigated, as both the monomers and their homopolymers are soluble in a wide variety of solvents, in contrast to methyl or ethyl ester polymers whose solubility in organic solvents com patible with mandatory anionic polymerization conditions is low, due to their high susceptibility to crystallize.…”