Cyclic monomers bearing either vinyl or exomethylene groups have the ability to be polymerized through a radical pathway via a ring-opening mechanism (addition–fragmentation process), leading to the ...introduction of functionalities in the polymer backbone. Radical ring-opening polymerization (rROP) combines the advantages of both ring-opening polymerization and radical polymerization, that is the preparation of polymers bearing heteroatoms in the backbone but with the ease and robustness of a radical process. This current review presents a comprehensive description of rROP by detailing: (i) the various monomers that polymerize through rROP; (ii) the main parameters that govern the rROP mechanism; (iii) the copolymerization by conventional or controlled/living radical polymerization between rROP monomers and traditional vinyl monomers to obtain copolymers with advanced properties; (iv) the different applications (low shrinkage materials and preparation of (bio)degradable materials) of rROP monomer-containing materials, and (v) the main alternatives to rROP to induce degradability to materials obtained by a radical polymerization.
Aqueous emulsion copolymerizations of dibenzoc,eoxepane‐5‐thione (DOT) were performed with n‐butyl acrylate (BA), styrene (S) and a combination of both. In all cases, stable latexes were obtained in ...less than two hours under conventional conditions; that is in the presence of sodium dodecyl sulfate (SDS) used as surfactant and potassium persulfate (KPS) as initiator. A limited solubility of DOT in BA was observed compared to S, yielding to a more homogeneous integration of DOT units in the PS latex. In both cases, the copolymer could be easily degraded under basic conditions. Emulsion terpolymerization between DOT, BA and S allowed us to produce stable latexes not only composed of degradable chains but also featuring a broad range of glass transition temperatures.
Emulsion copolymerization of dibenzoc,eoxepane‐5‐thione (DOT) with either styrene, n‐butyl acrylate or a mixture of both was carried out in water using sodium dodecyl sulfate (SDS) as surfactant and potassium persulfate (KPS) as initiator. Stable waterborne particles of vinylic polymers (blue) bearing cleavable thioester units (red) along the chains were obtained. The polymer chains were degraded to oligomers using a strong base (1,5,7‐triazabicyclo4.4.0dec‐5‐ene) or isopropylamine.
2-Methylene-1,3-dioxepane (MDO) and different vinyl ether (VE) monomers were successfully copolymerized by free-radical radical ring-opening copolymerization (rROP) to yield P(MDO-co-VE) copolymers ...with M n = 7 000–13 000 g·mol–1 and high molar fractions of MDO (F MDO = 0.7–0.9). By using VE derivatives of different aqueous solubilities or by grafting PEG chains onto the copolymers by “click” chemistry via azide-containing VE units, hydrophobic, amphiphilic and water-soluble copolymers were obtained. The different copolymers were then formulated into nanoparticles by nanoprecipitation using Pluronics for hydrophobic copolymers, without surfactant for amphiphilic copolymers, or blended with PMDO for water-soluble copolymers. Most of the copolymers led to nanoparticles with average diameters in the 130–250 nm with narrow particle size distributions and satisfying colloidal stability for a period of at least 1–2 weeks and up to 6 months. The copolymers were successfully degraded under accelerated, hydrolytic or enzymatic conditions. Hydrophobic copolymers led to degradation kinetics in PBS similar to that of PCL and complete degradation (−95% in M n decrease) was observed in the presence of enzymes (lipases). Preliminary cytotoxicity assays were performed on endothelial cells (HUVEC) and macrophages (J774.A1) and revealed high cell viabilities at 0.1 mg·mL–1.
The radical ring-opening polymerization (rROP) of cyclic ketene acetals (CKAs) by free radical or controlled radical mechanisms attracts considerable research interest as it presents an alternative ...route for the synthesis of aliphatic polyesters. These monomers can undergo radical addition to their C=C double bonds which subsequently leads to propagation by ring opening. CKA/vinyl monomer copolymerization appears to be an elegant method to produce partially or fully degradable copolymers depending on the proportion of the ester functionality incorporated into the copolymer backbone. Although this approach seems promising, some important limitations still remain. Owing to DFT calculations, we are now able to understand the reactivity of CKAs and common vinyl monomers. Indeed, the calculations confirm that cross-addition is not a key parameter for the copolymerization and the reactivity ratios are linked to the homopolymerization rate coefficients of the comonomer pair. In particular, it was demonstrated that trifluoromethyl vinyl acetate (CF
3
VAc) should provide alternating copolymers. These structures were confirmed experimentally with reactivity ratios close to 0 for the MDO/CF
3
VAc system (MDO = 2-methylene-1,3-dioxepane). A solid understanding of the reactivity of CKA monomers which allows for the tunable incorporation of main-chain functionalities into copolymers would open up exciting prospects in the field of degradable materials.
The ring-opening polymerization of cyclic ketene acetals (CKAs) and vinyl monomers is an elegant method to produce degradable copolymers. Owing to DFT calculations, we are now able to better understand the reactivity of CKAs & common vinyl monomers.
Controlled poly(acrylic acid) homopolymers were synthesized for the first time by direct nitroxide-mediated polymerization of acrylic acid. The polymerizations were performed in 1,4-dioxane solution ...at 120 °C, using an alkoxyamine initiator based on the N-tert-butyl-N-(1-diethyl phosphono-2,2-dimethyl propyl) nitroxide, SG1. The kinetics were controlled by the addition of free nitroxide at the beginning of the polymerization and the optimal amount was 9 mol % with respect to the initiator. In this case, whatever the initiator concentration, all polymerizations exhibited the same rate and conversion reached 85−90% within 5 h. Although the rate constant of propagation of acrylic acid is very large, its reactivity is moderated by a low activation−deactivation equilibrium constant between active macroradicals and SG1-capped dormant chains. Various alkoxyamine concentrations were investigated to target different molar masses. At high initiator concentrations, the number-average molar mass, M n, increased linearly with monomer conversion and followed the theoretical values; the polydispersity indexes ranged between 1.3 and 1.5. At low initiator concentration (high target M n), a deviation from linearity was observed in the M n vs conversion plot and was clearly assigned to chain transfer to 1,4-dioxane. From these results, the best experimental conditions to obtain well-defined homopolymers with the minimum amount of dead chains were identified.
Amphiphilic hairy nanoparticles are prepared in a one step, batch, heterogeneous polymerization of styrene or n-butyl acrylate, using a water-soluble poly(sodium acrylate) alkoxyamine macroinitiator ...based on the SG1 nitroxide.
The simple, one step synthesis of aqueous suspensions of amphiphilic nanoparticles is presented. Those particles are prepared in the batch heterophase polymerization of styrene or n-butyl acrylate, ...using a water-soluble poly(sodium acrylate) alkoxyamine macroinitiator. The nitroxidemediated controlled growth of the hydrophobic block leads to the formation of poly(sodium acrylate)-b-polystyrene or poly(sodium acrylate)-b-poly(n-butyl acrylate) amphiphilic diblock copolymers, able to self-assemble in water simultaneously to the growth step. When the diblock copolymers become strongly asymmetrical, with a short poly(sodium acrylate) block and a long hydrophobic one, the formed hairy nanoparticles are analogous to amphiphilic diblock copolymer crew-cut micelles.
Simulations of conversion versus time, molecular weight ($\overline M _{\rm n}$), polydispersity index (PDI), and living fractions versus conversion plots are performed using the PREDICI software, to ...study the influence of several kinetic parameters on the living and controlled character of nitroxide‐mediated polymerization (NMP). In particular, the crucial role of the main equilibrium represented by both kd and kc (the rate coefficients respectively of dissociation and recombination) is highlighted. On the other hand, the importance of the initiation step, the targeted $\overline M _{\rm n}$ value, and the initial excess of free nitroxide are also demonstrated. It is further proved that side reactions, such as disproportionation and transfer to solvent, have a strong impact on the polymerization characteristics.
The influence of various rate coefficients on both the kinetics and the controlled character of the reaction as well as the livingness of polymers obtained by nitroxide‐mediated polymerization (NMP) are studied using the program package PREDICI. These simulations result in very interesting guidelines, which can help predict, prior to any experiment, the optimum experimental conditions needed for specific properties, such as living fraction values.
Aqueous emulsion copolymerizations of dibenzoc,eoxepane‐5‐thione (DOT) were performed with n‐butyl acrylate (BA), styrene (S) and a combination of both. In all cases, stable latexes were obtained in ...less than two hours under conventional conditions; that is in the presence of sodium dodecyl sulfate (SDS) used as surfactant and potassium persulfate (KPS) as initiator. A limited solubility of DOT in BA was observed compared to S, yielding to a more homogeneous integration of DOT units in the PS latex. In both cases, the copolymer could be easily degraded under basic conditions. Emulsion terpolymerization between DOT, BA and S allowed us to produce stable latexes not only composed of degradable chains but also featuring a broad range of glass transition temperatures.
Emulsion copolymerization of dibenzoc,eoxepane‐5‐thione (DOT) with either styrene, n‐butyl acrylate or a mixture of both was carried out in water using sodium dodecyl sulfate (SDS) as surfactant and potassium persulfate (KPS) as initiator. Stable waterborne particles of vinylic polymers (blue) bearing cleavable thioester units (red) along the chains were obtained. The polymer chains were degraded to oligomers using a strong base (1,5,7‐triazabicyclo4.4.0dec‐5‐ene) or isopropylamine.
PDF
