Mechanistic transformation approach has been widely applied in polymer synthesis due to its unique feature combining structurally different polymers prepared by different polymerization mechanisms.Reported methods for...Mechanistic transformation approach has been widely applied in polymer synthesis due to its unique feature combining structurally different polymers prepared by different polymerization mechanisms.Reported methods for the formation of block and graft copolymers through mechanistic transformation involve almost all polymerizations modes.However,certain polymerization processes require extensive purification processes,which can be time-consuming and problematic.Recent developments on controlled/living polymerizations involving radical and cationic mechanisms with the ability to control molecular weight and functionality led to new pathways for mechanistic transformations.In this mini-review,we systematically discussed relevant advances in the field through three main titles namely(i)from radical to cationic mechanism,(ii)from cationic to radical mechanism,and(iii)application of specific catalyst systems for both radical and cationic polymerizations.展开更多
There are presently two ways to realize “controlled/living radical polymerization”: one is by a reversible termination or reversible chain transfer to make active polymer chains continuously propagate; the other is ...There are presently two ways to realize “controlled/living radical polymerization”: one is by a reversible termination or reversible chain transfer to make active polymer chains continuously propagate; the other is by a physical method to suppress chain termination and to prolong radical lifetime. Here we report a new method called Graduation Initiating Radical Polymerization System for realizing “controlled/living radical polymerization”. Its principle and experimental setup are as follows: firstly, initiatable groups(i.e. peroxide groups) were introduced onto the polymer substrates like LDPE film by photo-oxidation reaction; secondly, the films carried peroxide groups were put and fixed to the bottom of polymerization bottle containing monomer and solvent. Afterwards, they were made to produce radicals(by heating or reductive agent), and finally the system polymerization was initiated. Once these radicals are produced on the surface of these films, they will undergo three different processes: terminating by combination, diffusing to monomer solution and taking in monomers(polymerizing). The reactive diffusion makes this system produce “two graduation”: one is the graduation of radical concentration(i.e. the farther away from the surface of the film, the lower radical concentration); the other is the length-graduation of living chains,\{i.e.\} the farther away from the surface of the film the longer the propagating chains. By this way, we could obtain a polymerization field where the radical concentration is very low and there are no primary free radicals approximately, which are benefit to realize “controlled/living radical polymerization”. This communication reports the first experimental results based on the above idea: with benzophenone(BP) as photo-catalyst and peroxide groups introduced on the LDPE surface in a concentration 10^-8 mol/cm^2; by these peroxided films as the sources of free radicals, polyacrylamide and polyacrylic acid were obtained with molecular weights more than 20 millions展开更多
The bulk ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） by various phosphoric acids using phenylmethanol as the initiator was conducted. 1, 1＇-bi-2-Naphthol （BINOL）-based phosphoric acid was found...The bulk ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） by various phosphoric acids using phenylmethanol as the initiator was conducted. 1, 1＇-bi-2-Naphthol （BINOL）-based phosphoric acid was found to be an effective organocatalyst for ROP leading to polyesters at 90℃. The overall conversion to poly（ε-caprolactone） was more than 96% and poly（ε-caprolactone） with Mw of 8400 and polydispersity index of 1.13 was obtained. IH NMR spectra of oligomers demonstrated the quantitative incorporation of the protic initiator in the polymer chains and showed that transesterification reactions did not occur to a significant extent. The controlled polymerization was indicated by the linear relationships between the number-average molar mass and monomer conversion or monomer-to-initiator ratio. In addition, the present protocol provided an easy-to-handle, inexpensive and environmentally benign entry for the synthesis of biodegradable materials as well as polyesters for biomedical applications.展开更多
文摘Mechanistic transformation approach has been widely applied in polymer synthesis due to its unique feature combining structurally different polymers prepared by different polymerization mechanisms.Reported methods for the formation of block and graft copolymers through mechanistic transformation involve almost all polymerizations modes.However,certain polymerization processes require extensive purification processes,which can be time-consuming and problematic.Recent developments on controlled/living polymerizations involving radical and cationic mechanisms with the ability to control molecular weight and functionality led to new pathways for mechanistic transformations.In this mini-review,we systematically discussed relevant advances in the field through three main titles namely(i)from radical to cationic mechanism,(ii)from cationic to radical mechanism,and(iii)application of specific catalyst systems for both radical and cationic polymerizations.
文摘There are presently two ways to realize “controlled/living radical polymerization”: one is by a reversible termination or reversible chain transfer to make active polymer chains continuously propagate; the other is by a physical method to suppress chain termination and to prolong radical lifetime. Here we report a new method called Graduation Initiating Radical Polymerization System for realizing “controlled/living radical polymerization”. Its principle and experimental setup are as follows: firstly, initiatable groups(i.e. peroxide groups) were introduced onto the polymer substrates like LDPE film by photo-oxidation reaction; secondly, the films carried peroxide groups were put and fixed to the bottom of polymerization bottle containing monomer and solvent. Afterwards, they were made to produce radicals(by heating or reductive agent), and finally the system polymerization was initiated. Once these radicals are produced on the surface of these films, they will undergo three different processes: terminating by combination, diffusing to monomer solution and taking in monomers(polymerizing). The reactive diffusion makes this system produce “two graduation”: one is the graduation of radical concentration(i.e. the farther away from the surface of the film, the lower radical concentration); the other is the length-graduation of living chains,\{i.e.\} the farther away from the surface of the film the longer the propagating chains. By this way, we could obtain a polymerization field where the radical concentration is very low and there are no primary free radicals approximately, which are benefit to realize “controlled/living radical polymerization”. This communication reports the first experimental results based on the above idea: with benzophenone(BP) as photo-catalyst and peroxide groups introduced on the LDPE surface in a concentration 10^-8 mol/cm^2; by these peroxided films as the sources of free radicals, polyacrylamide and polyacrylic acid were obtained with molecular weights more than 20 millions
基金supported by the Fundamental Research Funds for the Central Universities (DL11CB06)
文摘The bulk ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） by various phosphoric acids using phenylmethanol as the initiator was conducted. 1, 1＇-bi-2-Naphthol （BINOL）-based phosphoric acid was found to be an effective organocatalyst for ROP leading to polyesters at 90℃. The overall conversion to poly（ε-caprolactone） was more than 96% and poly（ε-caprolactone） with Mw of 8400 and polydispersity index of 1.13 was obtained. IH NMR spectra of oligomers demonstrated the quantitative incorporation of the protic initiator in the polymer chains and showed that transesterification reactions did not occur to a significant extent. The controlled polymerization was indicated by the linear relationships between the number-average molar mass and monomer conversion or monomer-to-initiator ratio. In addition, the present protocol provided an easy-to-handle, inexpensive and environmentally benign entry for the synthesis of biodegradable materials as well as polyesters for biomedical applications.
