Yan Shi

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Name: 石艳; Yan Shi

Organization: Beijing University of Chemical Technology , China

Department: State Key Laboratory of Chemical Resource Engineering

Title: Associate Professor(PhD)

TOPICS

Polymer

Dendrimers Atom Transfer Radical Polymerization Radical Polymerization RAFT Block Copolymer

Organic Chemistry

Chemicals
References

Helically twining polymerization for constructing polymeric double helices

Co-reporter:Huajun Huang;Song Hong;Junya Liang;Jianping Deng

Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 37) pp:5726-5733

Publication Date(Web):2017/09/26

DOI:10.1039/C7PY00729A

The double helix is one of the most basic and exquisite architectures in nature, and thus has received much attention in multiple disciplines. However, the types of artificial polymeric double helices and their synthetic methods are severely limited. The present contribution develops a novel 3-step methodology for preparing double helices consisting of helical substituted polyacetylenes (DHSPs): (1) an optically inactive helical polymer is synthesized using an achiral monomer; (2) the as-obtained polymer is induced to form a one-handed helix by “locking” a chiral monomer in the helical grooves; (3) the “locked” chiral monomer undergoes helically twining polymerization along the pre-formed one-handed helical polymer chains, thereby constructing the DHSPs. Circular dichroism and UV-vis absorption spectra in combination with high resolution TEM images demonstrate the optical activity, double helical structure, and helix sense of the DHSPs. The convenient synthetic strategy is expected to provide various kinds of double helical polymers.

Hexamethylphosphoramide as a highly reactive catalyst for the reversible-deactivation radical polymerization of MMA with an in situ formed alkyl iodide initiator

Co-reporter:Yan-an Wang;Zhifeng Fu;Wantai Yang

Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 39) pp:6073-6085

Publication Date(Web):2017/10/10

DOI:10.1039/C7PY01186E

Hexamethylphosphoramide (HMPA) has been found to be a novel and highly efficient organic catalyst for the reversible-deactivation radical polymerization (RDRP) of methyl methacrylate (MMA) with an in situ formed alkyl iodide initiator. The polymerization results exhibited typical features of “living”/controlled radical polymerization. The polymerization process efficiently controls the molecular weight and chemical structure of the resultant poly(methyl methacrylate) (PMMA). Furthermore, the inhibition period was shortened and the polymerization rate was increased upon the addition of HMPA as compared to blank controls. Due to the high reactivity of HMPA, the molecular weight and molecular weight distribution of the resultant PMMA were well controlled at high monomer conversions at mild temperatures (Mw/Mn = 1.12–1.22, 60–70 °C). Notably, high-molecular-weight PMMA with a narrow molecular weight distribution were successfully obtained (Mn up to 104 000, Mw/Mn = 1.34). The living feature of the obtained polymers was confirmed by chain extension and block copolymerization. The mechanism for the controlled polymerization catalyzed by HMPA was also discussed. In brief, HMPA as a catalyst for RDRP with in situ formed alkyl iodide not only could simplify the polymerization process but also would be applicable as a powerful and robust method for well-defined polymers.

Multi-responsive fluorescence of amphiphilic diblock copolymer containing carboxylate azobenzene and N-isopropylacrylamide

Co-reporter:Hao Ren, Dong Chen, Yan Shi, Haifeng Yu, Zhifeng Fu

Polymer 2016 Volume 97() pp:533-542

Publication Date(Web):5 August 2016

DOI:10.1016/j.polymer.2016.05.074

•Micellization induced fluorescence in azo-containing block copolymer is investigated.•The mechanism relies on self-organization structure of the block copolymer.•The acquired fluorescence intensity can be adjusted by UV, pH and temperature.One amphiphilic diblock copolymer poly(NIPAm-b-M6AzCOONa) with well-defined structure was synthesized by RAFT polymerization, in which N-isopropylacrylamide (NIPAM) was introduced as one thermoresponsive unit, and 6-[4-(4-sodium carboxylatephenylazo)phenoxyl]hexyl methacrylate (M6AzCOONa) was designed as pH-, UV-responsive and fluorescent units. The block copolymer was non-fluorescent in good solvent, but showed fluorescence emission when it formed micelle-like structures in water. The acquired fluorescence can be adjusted by UV or pH, which was strongly related to the aggregation tightness and size of the micelles. The block copolymer also showed reversible fluorescent enhancement in a large range of pH value (pH = 3–11) driven by thermally-induced coil-to-globule transition due to the existence of the PNIPAm block, which leads to a more closely-tightened aggregation of azobenzene moieties. These multiple-responsive fluorescence behaviors enable the amphiphilic block copolymer to find its applications for wide-pH-range fluorescence thermometer and fluorescence probe.

A carboxylic azo monomer and its homopolymer: synthesis, self-organization and fluorescence behaviour in solution

Co-reporter:Hao Ren, Dong Chen, Yan Shi, Haifeng Yu and Zhifeng Fu

Polymer Chemistry 2015 vol. 6(Issue 2) pp:270-277

Publication Date(Web):09 Sep 2014

DOI:10.1039/C4PY01062K

We report special self-organization and fluorescence emission behaviours of a carboxylic azo monomer, 6-[4-(4-carboxylphenylazo)phenoxyl]hexyl methacrylate (M6AzCOOH), and its homopolymer (PM6AzCOOH) in solution. The monomer M6AzCOOH and its homopolymer PM6AzCOOH were non-fluorescent in N,N-dimethyl formamide (DMF) solution but became fluorescent, induced by the addition of water. The intensity of fluorescence emission increased with the amount of water in the mixed solvent and was sensitive to the pH value of the solution. The transmission electron microscopy (TEM) image reflected that vesicle-like structures formed due to the self-organization of PM6AzCOOH in water–DMF mixed solvent, and these structures changed into other forms of aggregation when the pH value of the solution was modified. The photoresponsive behaviour of the homopolymer in solution was investigated upon UV irradiation, demonstrating that trans–cis isomerization of azobenzene was hindered by the formation of aggregation and the change of aggregation form was responsible for the fluorescence emission behaviours.

Reverse iodine transfer polymerization (RITP) of chloroprene

Co-reporter:Jia Hui, Yan Shi, Tao Li, Jie Wu and Zhifeng Fu

RSC Advances 2015 vol. 5(Issue 55) pp:44326-44335

Publication Date(Web):08 May 2015

DOI:10.1039/C5RA04874E

Reversible-deactivation radical polymerization (RDRP) of chloroprene (2-chloro-1,3-butadiene, CP) using reverse iodine transfer polymerization (RITP) has been demonstrated for the first time. Reverse iodine transfer polymerizations of CP were studied in benzene at 50 °C using 2,2′-azobis(isoheptonitrile) (ABVN) as a radical initiator, where a molar ratio ABVN/I2 = 1.7 was used. The process efficiently controls the molar mass (characterized by size exclusion chromatography, SEC) and the structure of the polymer (confirmed by 1H NMR spectra). For example, polychloroprene (PCP) samples of Mn,SEC = 4900 g mol−1 and Mw/Mn = 1.73 (Mn,th = 4800 g mol−1), Mn,SEC = 7300 g mol−1 and Mw/Mn = 1.89 (Mn,th = 7300 g mol−1), and Mn,SEC = 9000 g mol−1 and Mw/Mn = 1.86 (Mn,th = 9300 g mol−1) were successfully obtained. Furthermore, the influence of solvent, initiator and temperature were studied. Last, the controlled nature of the polymer was confirmed by the preparation of polychloroprene-b-polystyrene (PCP-b-PSt) and polychloroprene-b-poly(methyl methacrylate) (PCP-b-PMMA) diblock copolymers.

Polymerization Mechanism in the Presence of 1,1-Diphenylethylene Part 2: Synthesis and Characterization of PMA and PSt

Co-reporter:Minjian Zhao;Zhifeng Fu;Wantai Yang

Macromolecular Chemistry and Physics 2015 Volume 216( Issue 22) pp:2202-2210

Publication Date(Web):

DOI:10.1002/macp.201500249

Reversible-deactivation radical polymerization of chloroprene and the synthesis of novel polychloroprene-based block copolymers by the RAFT approach

Co-reporter:Jia Hui, Zhijiao Dong, Yan Shi, Zhifeng Fu and Wantai Yang

RSC Advances 2014 vol. 4(Issue 98) pp:55529-55538

Publication Date(Web):02 Oct 2014

DOI:10.1039/C4RA08715A

Reversible addition–fragmentation chain transfer (RAFT) polymerization of the reactive monomer chloroprene (2-chloro-1,3-butadiene) mediated by ethyl 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate (EPDTB), 4-cyano-4-(phenylcarbonothioylthio) pentanoic acid (CPDTB) and dibenzyl trithiocarbonate (DBTTC) was investigated in benzene using 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. Polychloroprene (PCP) chains with predetermined molecular weights and low molar mass dispersities were synthesized by RAFT polymerization using EPDTB and CPDTB. The work described here also showed for the first time that well-defined polystyrene-block-polychloroprene (PSt-b-PCP) and poly(methyl methacrylate)-block-polychloroprene (PMMA-b-PCP) with controlled number averaged molecular weights and molecular weight distributions can be prepared in solution polymerization, employing EPDTB and 2-cyanoprop-2-yl dithiobenzoate (CPDB), respectively, as the initial RAFT agent. The success of the block copolymerization was showed by the shift toward higher molar mass of the size exclusion chromatography (SEC) chromatograms recorded before and after block copolymerization. Structural confirmation of the diblock copolymers was accomplished by 1H NMR measurements. The results obtained from SEC analysis together with 1H NMR spectroscopy demonstrate the possibility to design and prepare well-defined PCP-based block copolymers.

Preparation of PMMA-b-PSt Block Copolymer via Seeded Emulsion Polymerization in the Presence of 1,1-Diphenylethylene

Co-reporter:Minjian Zhao;Zhifeng Fu ;Wantai Yang

Macromolecular Reaction Engineering 2014 Volume 8( Issue 8) pp:555-563

Publication Date(Web):

DOI:10.1002/mren.201300174

Abstract

Poly(methyl methacrylate)-b-poly(styrene) (PMMA-b-PSt) block copolymer is synthesized successfully via seeded emulsion polymerization in the presence of 1,1-diphenylethylene (DPE). First, emulsion polymerization of MMA is carried out with KPS as initiator in the presence of DPE, giving a DPE-containing PMMA precursor with the ability of reactivation by simply heating. The emulsion polymerization behavior of MMA in the presence of DPE is investigated. The second monomer styrene (St) is then polymerized in PMMA seed emulsion and the block copolymer is successfully obtained. The formation of PMMA-b-PSt block copolymer is confirmed by ¹H NMR and gel permeation chromatography. Dynamic light scattering is used to monitor the particle diameters, and suggests that the particles grow without secondary nucleation occurring.

Iodoform-mediated free radical emulsion polymerization of chloroprene

Co-reporter:Juming Gu;Xinhua Yan;Zhifeng Fu;Wantai Yang

Journal of Applied Polymer Science 2013 Volume 128( Issue 4) pp:2291-2296

Publication Date(Web):

DOI:10.1002/app.38082

Abstract

The free radical emulsion polymerization of chloroprene (CP) is carried out at 9°C using different amounts of iodoform as the chain transfer agent. The molecular weight of polychloroprene (PCP) can be regulated effectively by CHI₃. PCP suitable for use as an adhesive is obtained with 0.22–0.28 wt % CHI₃ and reaches even higher monomer conversion than when mercaptan is used as the chain transfer agent. The emulsion polymerization of CP with high amounts of CHI₃ (1.0–3.0 wt %) proceeds in a living polymerization manner. The molecular weight increases in proportion to the monomer conversion in the range of the whole polymerization process even up to very high monomer conversion. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Synthesis of amphiphilic heteroarm star-shaped polymer via free radical polymerization using polyfunctional chain transfer agent and its self-assembly behavior

Co-reporter:Meng-Qing Lv;Wan-Tai Yang ;Zhi-Feng Fu

Journal of Applied Polymer Science 2013 Volume 128( Issue 1) pp:332-339

Publication Date(Web):

DOI:10.1002/app.38173

Abstract

Amphiphilic heteroarm star-shaped polymers have important theoretical and practical significance. In this work, amphiphilic heteroarm star-shaped polymer was synthesized by the use of polyfunctional chain transfer agent via sequential free radical polymerization in two steps. First, conventional free radical polymerization of methyl methacrylate (MMA) initiated by 2,2′-azobis (isobutyronitrile) (AIBN) was carried out in the presence of polyfunctional chain transfer agent, pentaerythritol-tertrakis (3-mercaptopropinate) (PETMP). At appropriate monomer conversion, about two-arm s-PMMA having two residual thiol groups at the chain center was obtained. Second, the s-PMMA obtained above was used as macro-chain-transfer agent for free radical polymerization of acrylic acid (AA). The heteroarm star-shaped polymer with the hydrophobic PMMA segment and the hydrophilic PAA segment was obtained. The successful synthesis of heteroarm star-shaped polymers, (PMMA)₂(AA)₂, was confirmed by ¹H-NMR and its self-assembly behavior in different solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Polymerization Mechanism of MMA in the Presence of 1,1-Diphenylethylene

Co-reporter:Minjian Zhao;Dong Chen;Wantai Yang ;Zhifeng Fu

Macromolecular Chemistry and Physics 2013 Volume 214( Issue 15) pp:1688-1698

Publication Date(Web):

DOI:10.1002/macp.201300260

Polymer nanoparticles with dendrimer-Ag shell and its application in catalysis

Co-reporter:Gaofei Dang, Yan Shi, Zhifeng Fu, Wantai Yang

Particuology 2013 Volume 11(Issue 3) pp:346-352

Publication Date(Web):June 2013

DOI:10.1016/j.partic.2011.06.012

Polymer nanoparticles with dendrimer-Ag shell were prepared and their application in catalytic reduction of 4-nitrophenol (4-NP) was investigated. Cross-linked polystyrene (PS) microspheres were prepared through dispersion copolymerization of styrene, acrylic acid and crosslinking monomer 1, 2-divinylbenzene. PS microspheres with average size of 450 nm and narrow size distribution were used as support for the immobilization of dendrimer-Ag shell. The polyamidoamine (PAMAM) dendrimer shell was successively grafted onto the surface of PS microspheres through repetitive Michael addition reaction of methyl acrylate (MA) and amidation of the obtained esters with large excess of ethylenediamine (EDA). Silver nanoparticles were formed directly inside the PAMAM shell through reduction with NaBH4. The resulting PS@PAMAM-Ag nanoparticles were packed in a stainless steel column and used successfully for catalytic reduction of 4-NP. This technique for packing catalytic polymer particles in a column could improve the efficiency of using the metal catalyst and the tedious separation in catalytic reaction.Graphical abstractSynthesis and application of PS@PAMAM-Ag nanoparticles.Highlights► Polymer nanoparticles with dendrimer-Ag shell were prepared. ► Catalytic ability was investigated in column. ► Packing catalytic polymer particles in column improved the efficiency.

Synthesis and characterization of Q-PEO-b-PVBC and Q-PEO-b-(PVBC-grad-PS) combined RAFT polymerization and post-polymerization quaternization

Co-reporter:Zhijiao Dong;Zhifeng Fu;Wantai Yang

Journal of Polymer Research 2012 Volume 19( Issue 9) pp:

Publication Date(Web):2012 September

DOI:10.1007/s10965-012-9953-y

Well defined amphiphilic block copolymers PEO-b-PVBC and PEO-b-(PVBC-grad-PS) were successfully synthesized via RAFT polymerization with PEO Macro-CTA as RAFT agent, AIBN as initiator, 4-vinylbenzyl chloride as monomer or 4-vinylbenzyl chloride and styrene as comonomers. The PEO Macro-CTA were synthesized through two steps. The degree of capping efficiency for PEO Macro-CTA can be increased to more than 80 % by changing the reaction conditions. Double hydrophilic block copolymers Q-PEO-b-PVBC was obtained by the quaternization of PEO-b-PVBC with triethylamine. PVBC-co-PS was synthesized via RAFT polymerization using 2-(ethoxycarbonyl) prop-2-yl dithiobenzoate as RAFT agent. The distributions of VBC and St units in the copolymers were investigated. The high reactivity of polymeric terminal radicals towards VBC in this system (rVBC = 1.50 and rSt = 0.61) resulted in the spontaneous formation of gradient copolymers. After quaternization of the PEO-b-(PVBC-grad-PS), the novel macromolecular architecture were obtained, which was consisted of the total hydrophilic block PEO and cationic amphiphilic gradient copolymer block.

Emulsion polymerization of styrene using irreversible addition–fragmentation chain transfer agents: effect on the course of the polymerization and molecular weight

Co-reporter:Li An;Chen Gao;Xinhua Yan;Zhifeng Fu;Wantai Yang

Colloid and Polymer Science 2012 Volume 290( Issue 8) pp:719-729

Publication Date(Web):2012 June

DOI:10.1007/s00396-012-2590-5

The emulsion polymerization of styrene with three different chain transfer agents (CTAs) based on irreversible addition–fragmentation chain transfer (AFCT) mechanism was first reported in this work. The influences of these irreversible AFCT agents on the rate of polymerization, particle size, and molecular weight were investigated. It was found that the intrinsic activity and desorption behaviors of the CTAs determined the efficiency for molecular weight control, rate of polymerization, and particle size in the emulsion polymerization. It has been demonstrated that the rate of polymerization and particle size decreased dramatically in the presence of the irreversible AFCT agents with high chain transfer constant (ethyl α-p-toluenesulfonyl-methacrylate), meanwhile, the molecular weight of the polystyrene could not be controlled well, whereas the irreversible AFCT agents with low chain transfer constant (butyl(2-phenylallyl)sulfane and 2,3-dichloropropene) had a slight effect on the polymerization rate, particle size, and were fairly well for molecular weight control over the whole conversion range in the emulsion polymerization of styrene. The average number of radicals per particle and the number-average molecular weight were calculated by classical radical emulsion polymerization theory, and the experimental results were in good agreement with the results of model calculations, when the irreversible AFCT agents were used as CTAs. The effect of chain transfer agents on the kinetics and nucleation in the emulsion polymerization of styrene can be attributed to desorption of chain-transferred radicals from the polymer particles. The results of this work show that butyl(2-phenylallyl)sulfane as CTA in emulsion polymerization of styrene provides the best balance between the rate of polymerization and the efficiency for molecular weight control conflicting tendencies.

Homo- and copolymerizations of ethylene and α-olefins in n-hexane catalyzed by Ni(ii)-α-diimine catalyst

Co-reporter:Xinhua Yan;Zhifeng Fu;Yingqi Li

Polymer Bulletin 2012 Volume 68( Issue 2) pp:327-339

Publication Date(Web):2012 January

DOI:10.1007/s00289-011-0540-x

Ni(II)-α-diimine catalyst [(2,6-i-Pr)2C6H3-DAB(An)]NiBr2 plus methylaluminoxane was successfully used in the homopolymerization of ethylene, 1-hexene, and 1-octene and the copolymerization of ethylene with 1-hexene and 1-octene in n-hexane. The polymerization of 1-octene was conducted in a controlled manner with a narrow molecular weight distribution (Mw/Mn = 1.2–1.5) and with the weight-average molecular weight increasing linearly with the monomer conversion. The molecular weights, Tg, Tm, branching degree, and density of the obtained (co)polymers were greatly controlled by ethylene pressure and polymerization temperature. Compared with that of ethylene homopolymer, the branching degree of the copolymers prepared by the copolymerization of ethylene with 1-hexene or 1-octene increased, whereas the molecular weight, density, Tm, and catalyst activity decreased. However, compared with those of the homopolymer of 1-hexene or 1-octene, the copolymer density, Tm, and catalyst activity increased, whereas the branching degree declined.

Immobilized copper catalyst for atom transfer radical addition and polymerization

Co-reporter:Lin Wang;Xinhua Yan;Zhifeng Fu;Yun Dai

Applied Organometallic Chemistry 2011 Volume 25( Issue 3) pp:190-197

Publication Date(Web):

DOI:10.1002/aoc.1739

Abstract

A novel multidentate amine grafted on silica gel and magnetic microsphere was prepared. Its chemical structure was confirmed by C¹³ NMR, XPS and FTIR, and the nitrogen content was determined by elemental analysis. It was also used as a ligand for CuCl and successfully catalyzed the atom transfer radical addition of both carbon tetrachloride (CCl₄) to methyl methacrylate and methyl trichloroacetate to styrene, repeatedly. The conversion and purity of the product were determined through gas chromatography and ¹H NMR, respectively. The immobilized copper catalyst complex was also used in atom transfer radical polymerization of styrene initiated by 1,1,1,3-tetrachloro-3-phenylpropane and methyl methacrylate initiated by methyl 2-methyl-2,4,4,4-tetrachlorobutyrate, respectively. Although the polymerization took place successfully, it did not proceed in a controlled fashion. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis of degradable copolymer networks containing hemiacetal components and well-defined backbones

Co-reporter:Xince Sui;Zhifeng Fu

Journal of Applied Polymer Science 2011 Volume 121( Issue 3) pp:1860-1865

Publication Date(Web):

DOI:10.1002/app.33589

Abstract

A novel copolymer network was prepared using divinyl ether bis[4-(vinyloxy)butyl] (4-methyl-1,3-phenylene) biscarbamate (BECT) as crosslinking agent. First, the backbone chains were synthesized by the copolymerization of acrylic acid (AA) and methyl methacrylate (MMA) using reversible addition-fragmentation chain-transfer technique. The molecular weight of poly(AA-co-MMA) was well-controlled, and the polydispersity was low. Carboxyl group on the poly(AA-co-MMA) chains then reacted with BECT in the presence of pyridinium p-toluenesulfonate, generating a copolymer network with hemiacetal component in the crosslinking segment. After being treated in strong acid, this copolymer network was able to be degraded owing to the hemiacetal structure, but the backbone chains remained intact. The copolymer network was stable in basic or neutral environment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis and application of novel degradable crosslinkers

Co-reporter:Xin Ce Sui, Zhi Feng Fu, Yan Shi

Chinese Chemical Letters 2011 Volume 22(Issue 3) pp:374-377

Publication Date(Web):March 2011

DOI:10.1016/j.cclet.2010.10.028

A novel divinyl ether was synthesized by a convenient method with high yield. Then the divinyl ether was combined with 2-hydroxyethyl methacrylate and acrylic acid, respectively, generating difunctional polymeric crosslinkers with (hemi)acetal structure that was labile in acid. The chemical structures of the divinyl ether and crosslinkers were confirmed by 1H NMR and elemental analysis. The crosslinkers were employed in free-radical polymerization to prepare polymer gel and gel particles. Due to the (hemi)acetal structure in the crosslinking segment, the polymer gel and particles exhibited degradable ability in strong acid.

Synthesis of amphiphilic diblock copolymers by direct radical polymerization of acrylic acid via DPE method

Co-reporter:Dong Lan;Dong Chen;Zhifeng Fu

Polymer Bulletin 2011 Volume 66( Issue 2) pp:175-185

Publication Date(Web):2011 January

DOI:10.1007/s00289-010-0263-4

Amphiphilic diblock copolymers, poly(methyl methacrylate)-b-poly(acrylic acid) (PMMA-b-PAA) was prepared by 1,1-diphenylethene (DPE) method. First, free radical polymerization of methyl methacrylate was carried out with AIBN as initiator in the presence of DPE, giving a DPE-containing PMMA precursor with controlled molecular weight. Amphiphilic diblock copolymer PMMA-b-PAA was then prepared by radical polymerization of acrylic acid (AA) in the presence of PMMA precursor. The formation of PMMA-b-PAA was confirmed by 1H NMR spectrum and gel permeation chromatography. Transmission electron microscopy and dynamic light scattering were used to detect the self-assembly behavior of the amphiphilic diblock polymers in methanol.

Study on atom transfer radical polymerization initiated by p-nitrophenyl initiator and synthesis of amino end-functionalized polymers thereof

Co-reporter:Tianyu Qu;Wenqian Cai;Zhifeng Fu

Macromolecular Research 2010 Volume 18( Issue 7) pp:623-629

Publication Date(Web):2010 July

DOI:10.1007/s13233-010-0703-x

Thermal Self-Initiation in Stable Free-Radical Polymerization of Styrene

Co-reporter:Yuejian Sun, Yaoying Wu, Liguo Chen, Zhifeng Fu and Yan Shi

Polymer Journal 2009 41(11) pp:954-960

Publication Date(Web):August 26, 2009

DOI:10.1295/polymj.PJ2008269

Stable free radical polymerization (SFRP) of styrene was carried out using bis(4-bromomethylbenzoyl)peroxide (BBMBPO)/4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy (HTEMPO) or 4,4′-azobis(4-cyanopentyl)-α-bromoisobutyrate (ABCBIB)/HTEMPO as bimolecular initiating system. It was found that the molecular weights of obtained polystyrenes were controlled by the concentration of HTEMPO. Besides those generated by the initiators, some polystyrene chains were formed via thermal initiation. Polystyrene chains generated by the initiator had initiating groups for atom transfer radical polymerization (ATRP) at their ends, so they grew to higher molecular weights in ATRP of styrene. While the molecular weights of polystyrene chains generated by thermal initiation kept constant in ATRP conditions because of their inert terminals for ATRP. The amount of polystyrenes generated by thermal initiation was investigated quantitatively via gel permeation chromatography technique.

Synthesis of poly(vinyl acetate) containing diblock copolymer by DPE method

Co-reporter:Dong Chen;Zhifeng Fu

Journal of Applied Polymer Science 2009 Volume 111( Issue 3) pp:1581-1587

Publication Date(Web):

DOI:10.1002/app.29164

Abstract

Diblock copolymer poly(methyl methacrylate)-b-poly(vinyl acetate) (PMMA-b-PVAc) was prepared by 1,1-diphenylethene (DPE) method. First, free-radical polymerization of methyl methacrylate was carried out with AIBN as initiator in the presence of DPE, giving a DPE containing PMMA precursor with controlled molecular weight. Second, vinyl acetate was polymerized in the presence of the PMMA precursor and AIBN, and PMMA-b-PVAc diblock copolymer with controlled molecular weight was obtained. The formation of PMMA-b-PVAc was confirmed by ¹H NMR spectrum. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to detect the self-assembly behavior of the diblock polymer in methanol. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Investigation on chain transfer reaction of benzene sulfonyl chloride in styrene radical polymerization

Co-reporter:Cuiping Li;Zhifeng Fu

Macromolecular Research 2009 Volume 17( Issue 8) pp:557-562

Publication Date(Web):2009 August

DOI:10.1007/BF03218908

The free radical polymerization of styrene was initiated with azobis(isobutyronitrile) in the presence of benzene sulfonyl chloride. Analysis of the terminal structures of the obtained polystyrene with1H NMR spectroscopy revealed the presence of a phenylsulfonyl group at the α-end and a chlorine atom at the ω-end of each polystyrene chain. The terminal chlorine atom in the polystyrene chains was further confirmed through atom transfer radical polymerization (ATRP) of styrene and methyl acrylate using the obtained polystyrenes as macroinitiators and CuCl/2,2′-bipyridine as the catalyst system. GPC traces of the products obtained in ATRP at different reaction times were clearly shifted to higher molecular weight direction, indicating that nearly all the macroinitiator chains initiated ATRP of the second monomers. In addition, the number-average molecular weights of the polystyrenes increased directly proportional to the monomer conversions, and agreed well with the theoretical ones.

Synthesis of densely grafted comblike copolymers

Co-reporter:Zhifeng Fu;Wuping Tao

Journal of Polymer Science Part A: Polymer Chemistry 2008 Volume 46( Issue 1) pp:362-372

Publication Date(Web):

DOI:10.1002/pola.22386

Abstract

Densely grafted copolymers were synthesized using the “grafting from” approach via the combination of reversible addition-fragment chain transfer polymerization (RAFT) and atom transfer radical polymerization (ATRP). First, a novel functional monomer, 2,3-di(2-bromoisobutyryloxy)ethyl acrylate (DBPPA), with two initiating groups for ATRP was synthesized. It was then polymerized via RAFT polymerization to give macroinitiators for ATRP with controlled molecular weights and narrow molecular weight distributions. Last, ATRP of styrene was carried out using poly(DBPPA)s as macroinitiators to prepare comblike poly(DBPPA)-graft-polystyrenes carrying double branches in each repeating unit of backbone via “grafting from” approach. Furthermore, poly(DBPPA)-graft-[polystyrene-block-poly(t-BA)]s and their hydrolyzed products poly(DBPPA)-graft-[polystyrene-block-poly(acrylic acid)]s were also successfully prepared. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 362–372, 2008

Synthesis of Amphiphilic Diblock Copolymers by DPE Method

Co-reporter:Dong Chen;Zhifeng Fu

Polymer Bulletin 2008 Volume 60( Issue 2-3) pp:259-269

Publication Date(Web):2008 March

DOI:10.1007/s00289-007-0873-7

Amphiphilic diblock copolymers, poly(methyl methacrylate)-b-poly(acrylic acid) (PMMA-b-PAA) and polystyrene-b-poly(acrylic acid) (PS-b-PAA), were prepared by 1,1-diphenylethene (DPE) method under mild conditions. Firstly, free radical polymerization of tert-butyl acrylate (tBA) was carried out with AIBN as initiator in the presence of DPE, giving a DPE-containing precursor, PtBA, with controlled molecular weight. Secondly, methyl methacrylate and styrene were polymerized in the presence of PtBA precursor, and PS-b-PtBA and PMMA-b-PtBA diblock copolymers with controlled molecular weights were obtained respectively. Finally, amphiphilic diblock copolymers, PMMA-b-PAA and PS-b-PAA, were prepared by hydrolysis of PS-b-PtBA and PMMA-b-PtBA. The formation of PS-b-PAA and PMMA-b-PAA was confirmed by 1H NMR. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to detect the self-assembly behavior of the amphiphilic diblock polymers in tetrahydrofuran (THF).