(S)-2-(ethyl propionate)-(O-ethyl xanthate)- and (S)-2-(Ethyl isobutyrate)-(O-ethyl xanthate)-mediated RAFT polymerization of vinyl acetate

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and (S)-2-(Ethyl isobutyrate)-(O-ethyl xanthate) (X2) were used as the reversible addition-fragmentation chain transfer (RAFT) agents for the radical polymerization of vinyl acetate (VAc). The former showed the better chain transfer ability in the polymerization at 60°C. Kinetic study with both RAFT agents showed pseudo-first order kinetics up to around 85% monomer conversion. Molecular weight of the resulting polymer increased linearly with increase in the monomer conversion up to around 85%. The observed molecular weights calculated from ¹H-NMR spectrum [M_n(NMR)] are close to the corresponding theoretical molecular weights [M_n(theor)]. The corresponding polydispersity index (PDI) of the resulting polymers remained almost constant at around 1.2 up to ∼ 65% monomer conversion and then increased gradually with the further increase in the monomer conversion. Chain-end analysis of the resulting polymers by ¹H-NMR showed clearly that polymerization started with the radical forming out of the xanthate mediator. The negligible homo-chain extension and the hetero-chain extension involving synthesis of poly(VAc)-b-poly(NVP) diblock copolymer were occurred. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) and (S)-2-(Ethyl isobutyrate)-(O-ethyl xanthate)-mediated RAFT polymerization of N-vinylpyrrolidone

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and the newly synthesized (S)-2-(ethyl isobutyrate)-(O-ethyl xanthate) (X2) were used as the reversible addition-fragmentation chain transfer (RAFT) agents for the radical polymerization of N-vinylpyrrolidone (NVP). The former showed the better chain transfer ability in the polymerization at 60 °C. Kinetics study with X1 shows the psuedo-first order kinetics upto 45% monomer conversion. Molecular weight (M _n) of the resulted polymer increases linearly with increase in the monomer conversion upto around 45%. Polydispersity of the corresponding poly(NVP)s increase gradually from 1.2 to 1.9 with increase in the monomer conversion. Chain-end analysis of the resulted polymer by ¹H NMR shows clearly that polymerization started with radical forming out of xanthate mediator. Living nature of the polymerization was confirmed from the successful homo chain extension experiment and also the hetero-chain extension experiment involving synthesis of poly(NVP)-b-polystyrene amphiphilic diblock copolymer.     

Synthesis of fluorescence poly(N-vinylpyrrolidone) via click chemistry using azide-terminated xanthate mediator (S)-2-(4-azidobutyl propionate)-(O-ethyl xanthate)

Azide-terminated xanthate RAFT agent (S)-2-(4-azidobutyl propionate)-(O-ethyl xanthate) has been synthesized and used for the controlled radical polymerization of N-vinylpyrrolidone (NVP). Kinetics study showed the pesudo first-order kinetics along with gradual increase in molecular weight (M_n) of the resulted polymer up to 69% conversion. Chain-end analysis of the resulted polymer by ¹H NMR showed the presence of the fragments of xanthate mediator at both chain ends. Successful chain extension has also been performed via the click reaction of alkyne-terminated PNVP with azide-terminated PNVP. Moreover, fluorescence pyrene-tagged PNVP has successfully been made via the click reaction of alkyne-functionalized pyrene with azide-terminated PNVP.     

Poly(dimethylsiloxane‐b‐styrene) diblock copolymers prepared by reversible addition‐fragmentation chain transfer polymerization: Kinetic model

Well‐defined polydimethylsiloxane‐block‐polystyrene (PDMS‐b‐PS) diblock copolymers were prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization using a functional PDMS‐macro RAFT agent. The RAFT polymerization kinetics was simulated by a mathematical model for the RAFT polymerization in a batch reactor based on the method of moments. The model described molecular weight, monomer conversion, and polydispersity index as a function of polymerization time. Good agreements in the polymerization kinetics were achieved for fitting the kinetic profiles with the developed model. In addition, the model was used to predict the effects of initiator concentration, chain transfer agent concentration, and monomer concentration on the RAFT polymerization kinetics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of 1,3‐benzodioxole end‐functionalized polymers via reversible addition–fragmentation chain transfer polymerization

Reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene was carried out in the presence of a novel RAFT reagent, bearing 1,3‐benzodioxole group, benzo [1,3]dioxole‐5‐carbodithioic acid benzo [1,3]dioxol‐5‐ylmethyl ester (BDCB), to prepare end‐functionalized polystyrene. The polymerization results showed that RAFT polymerization of styrene could be well controlled. Number–average molecular weight (M_n(GPC)) increased linearly with monomer conversion, and molecular weight distributions were narrow (M_w/M_n < 1.4). The successful reaction of chain extension and analysis of ¹H NMR spectra confirmed the existence of the functional 1,3‐benzodioxole group at the chain‐end of polystyrene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3535–3539, 2006     

Polymer chain extension in semibatch emulsion polymerization with RAFT‐based transfer agent: The influence of reaction conditions on polymerization rate and product properties

A mathematical model was developed for batch and semiemulsion polymerizations of styrene in the presence of a xanthate‐based RAFT agent. Zero–one kinetics was employed along with population balance equations to predict monomer conversion, molecular weight (MWD), and particle size (PSD) distributions in the presence of xanthate‐based RAFT agents. The effects of the transfer agent (AR), surfactant, initiator, and temperature were investigated. Monomer conversion, MWD, and PSD were found to be strongly affected by monomer feed rate. The polymerization rate (Rp), number average molecular weight (Mn) and particle size (r) decreased with increasing AR. With increases in surfactant and initiator concentrations Rp increased, whereas with increase in temperature Mn decreased, Rp increased and r increased. In semibatch mode, Mn and r increased with increase in monomer flow rate. By feeding the RAFT agent along with the monomer (F_M/F_AR = N_Mo/N_ARo = 100), Mn attained a constant value proportional to monomer/RAFT molar ratio. The observed retardation in polymerization and growth rates is due to the exit and re‐entry of small radicals. Thus, chain extension was successfully achieved in semibatch mode. The simulations compared well with our experimental data, and the model was able to accurately predict monomer conversion, Mn, MWD, and PSD of polymer products. Our simulations and experimental results show that monomer feed rate is suitable for controlling the PSD, and the initial concentration and the feed rate of AR for controlling the MWD and PSD. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ab initio reversible addition–fragmentation chain transfer emulsion polymerization of styrene/butyl acrylate mediated by poly(acrylic acid)‐block‐polystyrene trithiocarbonate

Ab initio reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of styrene/butyl acrylate was investigated with the trithiocarbonate macro‐RAFT agent poly(acrylic acid)‐block‐polystyrene (PAA‐b‐PS) as a stabilizer and a RAFT agent. Influences of the amount of ammonium persulfate (APS), the amount of PAA‐b‐PS and the mass ratio of monomers on emulsion polymerization and film properties are discussed. The particle morphology exhibited spherical‐like structure with particles of about 90 nm in diameter and relatively narrow particle size distribution characterized using transmission electron microscopy and dynamic laser scattering. Fourier transform infrared and ¹H NMR spectra showed that the styrene/butyl acrylate emulsion was successfully synthesized. The monomer conversion increased initially with increasing amount of APS, from 0.4 up to 0.8 wt%, and then decreased. The particle size increased and its distribution decreased gradually with increasing amount of APS. The monomer conversion increased from 76.83 to 94.21% as the amount of PAA‐b‐PS increased from 3 to 4 wt%, and then decreased with further increase of PAA‐b‐PS. The particle size decreased and its distribution increased with increasing amount of PAA‐b‐PS. The water resistance and solvent resistance of the polymer films initially increased and then decreased with decreasing mass ratio of butyl acrylate to styrene. © 2014 Society of Chemical Industry     

RAFT polymerization of N‐vinyl pyrrolidone using prop‐2‐ynyl morpholine‐4‐carbodithioate as a new chain transfer agent

RAFT polymerization of N‐vinyl pyrrolidone (NVP) has been investigated in the presence of chain transfer agent (CTA), i.e., prop‐2‐ynyl morpholine‐4‐carbodithioate (PMDC). The influence of reaction parameters such as monomer concentration [NVP], molar ratio of [CTA]/[AIBN, i.e., 2,2′‐azobis (2‐methylpropionitrile)] and [NVP]/[CTA], and temperature have been studied with regard to time and conversion limit. This study evidences the parameters leading to an excellent control of molecular weight and molar mass dispersity. NVP has been polymerized by maintaining molar ratio [NVP]: [PMDC]: [AIBN] = 100 : 1 : 0.2. Kinetics of the reaction was strongly influenced by both temperature and [CTA]/[AIBN] ratio and to a lesser extent by monomer concentration. The activation energy (E_a = 31.02 kJ mol^?1) and enthalpy of activation (ΔH^?= 28.29 kJ mol^?1) was in a good agreement to each other. The negative entropy of activation (ΔS^? = ?210.16 J mol^‐1K^‐1) shows that the movement of reactants are highly restricted at transition state during polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of poly(cyclohexene oxide)‐block‐polystyrene by combination of radical‐promoted cationic polymerization,atom transfer radical polymerization and click chemistry

The combination of radical‐promoted cationic polymerization, atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of poly(cyclohexene oxide)‐block‐polystyrene (PCHO‐b‐PSt). Alkyne end‐functionalized poly(cyclohexene oxide) (PCHO‐alkyne) was prepared by radical‐promoted cationic polymerization of cyclohexene oxide monomer in the presence of 1,2‐diphenyl‐2‐(2‐propynyloxy)‐1‐ethanone (B‐alkyne) and an onium salt, namely 1‐ethoxy‐2‐methylpyridinium hexafluorophosphate, as the initiating system. The B‐alkyne compound was synthesized using benzoin photoinitiator and propargyl bromide. Well‐defined bromine‐terminated polystyrene (PSt‐Br) was prepared by ATRP using 2‐oxo‐1,2‐diphenylethyl‐2‐bromopropanoate as initiator. Subsequently, the bromine chain end of PSt‐Br was converted to an azide group to obtain PSt‐N₃ by a simple nucleophilic substitution reaction. Then the coupling reaction between the azide end group in PSt‐N₃ and PCHO‐alkyne was performed with Cu(I) catalysis in order to obtain the PCHO‐b‐PSt block copolymer. The structures of all polymers were determined. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization of poly(HEMA‐co‐MMA)‐g‐POSS nanocomposites by combination of reversible addition fragmentation chain transfer polymerization and click chemistry

New hybrid poly(hydroxyethyl methacrylate‐co‐methyl methacrylate)‐g‐polyhedral oligosilsesquioxane [poly(HEMA‐co‐MMA)‐g‐POSS] nanocomposites were synthesized by the combination of reversible addition fragmentation chain transfer (RAFT) polymerization and click chemistry using a grafting to protocol. Initially, the random copolymer poly(HEMA‐co‐MMA) was prepared by RAFT polymerization of HEMA and MMA. Alkynyl side groups were introduced onto the polymeric backbones by esterification reaction between 4‐pentynoic acid and the hydroxyl groups on poly(HEMA‐co‐MMA). Azide‐substituted POSS (POSS? N₃) was prepared by the reaction of chloropropyl‐heptaisobutyl‐substituted POSS with NaN₃. The click reaction of poly(HEMA‐co‐MMA)‐alkyne and POSS? N₃ using CuBr/PMDEATA as a catalyst afforded poly(HEMA‐co‐MMA)‐g‐POSS. The structure of the organic/inorganic hybrid material was investigated by Fourier transformed infrared, ¹H‐NMR, and ²⁹Si‐NMR. The elemental mapping analysis of the hybrid using X‐ray photoelectron spectroscopy and EDX also suggest the formation of poly(HEMA‐co‐MMA)‐anchored POSS nanocomposites. The XRD spectrum of the nanocomposites gives evidence that the incorporation of POSS moiety leads to a hybrid physical structure. The morphological feature of the hybrid nanocomposites as captured by field emission scanning electron microscopy and transmission electron microscopic analyses indicate that a thick layer of polymer brushes was immobilized on the POSS cubic nanostructures. The gel permeation chromatography analysis of poly(HEMA‐co‐MMA) and poly(HEMA‐co‐MMA)‐g‐POSS further suggests the preparation of nanocomposites by the combination of RAFT and click chemistry. The thermogravimetric analysis revealed that the thermal property of the poly(HEMA‐co‐MMA) copolymer was significantly improved by the inclusion of POSS in the copolymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Highly efficient reversible addition–fragmentation chain‐transfer polymerization in ethanol/water via flow chemistry

Utilization of a flow reactor under high pressure allows highly efficient polymer synthesis via reversible addition–fragmentation chain‐transfer (RAFT ) polymerization in an aqueous system. Compared with the batch reaction, the flow reactor allows the RAFT polymerization to be performed in a high‐efficiency manner at the same temperature. The adjustable pressure of the system allows further elevation of the reaction temperature and hence faster polymerization. Other reaction parameters, such as flow rate and initiator concentration, were also well studied to tune the monomer conversion and the molar mass dispersity (?) of the obtained polymers. Gel permeation chromatography, nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopies (FTIR) were utilized to monitor the polymerization process. With the initiator concentration of 0.15 mmol L^?1, polymerization of poly(ethylene glycol) methyl ether methacrylate with monomer conversion of 52% at 100 °C under 73 bar can be achieved within 40 min with narrow molar mass dispersity (D) ? (<1.25). The strategy developed here provides a method to produce well‐defined polymers via RAFT polymerization with high efficiency in a continuous manner. © 2017 Society of Chemical Industry     

Preparation of well‐defined block copolymer having one polystyrene segment and another poly(styrene‐alt‐maleic anhydride) segment with RAFT polymerization

Block copolymers, polystyrene‐b‐poly(styrene‐co‐maleic anhydride), have been prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization technique using three different approaches: 1‐phenylethyl phenyldithioacetate (PEPDTA) directly as RAFT agent, mediated polystyrene (PS) block as the macromolecular PS‐RAFT agent and mediated poly(styrene‐maleic anhydride) (SMA) block with alternating sequence as the macromolecular SMA‐RAFT agent. Copolymers synthesized in the one‐step method using PEPDTA as RAFT agent possess one PS block and one SMA block with gradient structure. When the macromolecular RAFT agents are employed, copolymers with one PS block and one alternating SMA block can be produced. However, block copolymers with narrow molecular weight distribution (MWD) can only be obtained using the PS‐RAFT agent. The MWD deviates considerably from the typical RAFT polymerization system when the SMA is used as the RAFT agent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Controlled grafting of poly(vinyl acetate) onto starch via RAFT polymerization

A structure‐exact starch‐based xanthate agent was prepared and used as chain transfer agent to mediate RAFT polymerization of vinyl acetate, which offered a convenient way to well control the structure and composition of starch‐g‐poly(vinyl acetate). The structures of the intermediate and the polymer were verified with FTIR and ¹H‐NMR. Gel permeation chromatography measurement results indicated that the polymerization was performed as expected. It was found that the relationship between number average molecular weight and monomer conversion was linear. The polydispersity index of grafted side‐chain ranged from 1.19 to 1.53 and most of them were around 1.2. There was one more degradation stage appeared on the thermogravimetric analysis profile of starch‐g‐poly(vinyl acetate) than that of starch. TEM observation exhibited that the product was able to self‐assemble into micelles in aqueous solution, which suggested the copolymer was amphiphilic. Both the thermal and amphiphilic properties demonstrated the starch‐g‐poly(vinyl acetate) was successfully synthesized as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A new selenium-based RAFT agent for surface-initiated RAFT polymerization of 4-vinylpyridine

A new selenium-based reversible addition-fragmentation chain transfer (RAFT) agent, 4-cyanopentanoic acid diselenobenzoate (RAFT-Se), was synthesized and utilized in the surface-initiated RAFT polymerization of 4-vinylpyridine (4VP) on silicon substrate. The results indicate that the RAFT-Se can control the surface-initiated RAFT polymerization, as evidenced by the number-average molecular weight that increase linearly with monomer conversion, molecular weights that agreed well with the predicted values, and the relatively low polydispersity indexes. The surface-initiated RAFT polymerization with the RAFT-Se was the same polymerization mechanism as its analog, 4-cyanopentanoic acid dithiobenzoate (RAFT-S). The grafting density of the poly(4-vinylpyridine) brushes prepared in the presence of RAFT-Se (σ_RAFT-Se) and RAFT-S (σ_RAFT-S) was estimated to be about 0.51 and 0.66 chains/nm², respectively. In addition, the end of polymer chains on silicon substrate contains selenium element which may be useful in biosensor applications.     

Nanoporous well‐defined reversible addition–fragmentation chain transfer polymer of N‐acrylamido‐l‐tryptophan: synthesis and characterization

A nanoporous polymer with a chiral pendant chain of N‐acrylamido‐l ‐tryptophan was synthesized through a reversible addition–fragmentation chain transfer polymerization process using a dithiobenzoate derivative as chain transfer agent. The polymerization exhibited the usual characteristics of living processes, though slow polymerization rate and low percentage conversion for a chain extension experiment were observed. Depending on the monomer/chain transfer agent ratio, poly(N‐acrylamido‐l ‐tryptophan) with number‐average molecular weights between 640 and 4340 g mol^?1 and molar mass dispersities between 1.10 and 1.24 was obtained, as evidenced from gel permeation chromatography. Scanning electron microscopy images indicated that the polymer was porous. Nitrogen adsorption analysis of the polymer evidenced the presence of mesopores (2–19 nm) associated with micropores (0.45–2 nm) according to the Barrett–Joyner–Halenda method with a specific Brunauer–Emmett–Teller surface area of 22.98 m² g^?1. © 2013 Society of Chemical Industry     

Controlled/living RAFT polymerization of N‐phenyl maleimide and synthesis of its block copolymers

The controlled/living radical polymerization of N‐phenyl maleimide (NPMI) was achieved using 2,2′‐azobisisobutyronitrile as the initiator and 2‐cyanopropyl‐2‐yl dithiobenzoate as the reversible addition‐fragmentation chain transfer agent at 75°C in dichloroethane/ethylene carbonate (60/40, w/w) mixed solvent. The block copolymers of polystyrene‐b‐polyNPMI and poly(n‐butyl methacrylate)‐b‐polyNPMI were successfully prepared by chain extension from dithiobenzoate‐terminated polystyrene and poly (n‐butyl methacrylate) to NPMI, respectively. The obtained NPMI‐based (co)polymers were characterized by gel permeation chromatography and ¹H‐NMR spectroscopy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

RAFT synthesis of poly(N‐isopropylacrylamide) and poly(methacrylic acid) homopolymers and block copolymers: Kinetics and characterization

Reversible addition‐fragmentation chain transfer (RAFT) polymerization was used successfully to synthesize temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAAm), poly(methacrylic acid) (PMAA), and their temperature‐responsive block copolymers. Detailed RAFT polymerization kinetics of the homopolymers was studied. PNIPAAm and PMAA homopolymerization showed living characteristics that include a linear relationship between M _n and conversion, controlled molecular weights, and relatively narrow molecular weight distribution (PDI < 1.3). Furthermore, the homopolymers can be reactivated to produce block copolymers. The RAFT agent, carboxymethyl dithiobenzoate (CMDB), proved to control molecular weight and PDI. As the RAFT agent concentration increases, molecular weight and PDI decreased. However, CMDB showed evidence of having a relatively low chain transfer constant as well as degradation during polymerization. Solution of the block copolymers in phosphate buffered saline displayed temperature reversible characteristics at a lower critical solution temperature (LCST) transition of 31°C. A 5 wt % solution of the block copolymers form thermoreversible gels by a self‐assembly mechanism above the LCST. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1191–1201, 2006     

Preparation of poly(tert‐butyl acrylate)‐poly(acrylic acid) amphiphilic copolymers via radiation‐induced reversible addition–fragmentation chain transfer mediated polymerization of tert‐butyl acrylate

Poly(tert‐butyl acrylate) (PtBA) is a versatile hydrophobic macromolecule usually preferred in the development of new materials for a host of applications. PtBA homopolymers with well‐defined structure and controlled molecular weight in a wide range were successfully synthesized via radiation‐induced reversible addition–fragmentation chain transfer (RAFT) polymerization in the presence of a trithiocarbonate type RAFT agent. The polymerization of tBA was performed under ⁶⁰Co γ‐irradiation in the presence of 2‐(dodecylthiocarbonothioylthio)‐2‐methylpropionic acid (DDMAT) as the RAFT agent in toluene at room temperature with three [tBA]/[DDMAT] ratios (400, 600 and 1000) and different irradiation times. Radiation‐induced polymerization of tBA displayed controlled free radical polymerization characteristics: a narrow molecular weight distribution (M_w/M_n ~ 1.1), pseudo first order kinetics and controlled molecular weights. The system followed the RAFT polymerization mechanism even at very low amounts of RAFT agent ([tBA]/[DDMAT] = 1000), and molecular weights up to 113 900 with narrow dispersity (Ð =1.06) were obtained. PtBA was further hydrolysed into different amphiphilic PtBA‐co‐poly(acrylic acid) (PAA) copolymers by low (27.5%) and high (77.3%) degrees of hydrolysis. The pH sensitivity of the two copolymers was investigated by dynamic light scattering at pH 2 and pH 9 (above and below the pK_a value of PAA) and their hydrodynamic diameters and zeta potential values were determined. © 2020 Society of Chemical Industry     

Star graft copolymer via grafting‐onto strategy using a comb!ination of reversible addition–fragmentation chain transfer arm‐first technique and aldehyde–aminooxy click reaction

A facile synthetic pathway to a multi‐arm star graft polymer has been developed via a grafting‐onto strategy using a combination of a reversible addition–fragmentation chain transfer (RAFT) arm‐first technique and aldehyde–aminooxy click reaction. A star backbone bearing aldehyde groups was prepared by the RAFT copolymerization of acrolein (Ac), an existing commercial aldehyde‐bearing monomer, with styrene (St), followed by crosslinking of the resultant poly(St‐co‐Ac) macro‐RAFT agent using divinylbenzene. The aldehyde groups on the star backbone were then used as clickable sites to attach poly(ethylene glycol) (PEG) side chains via the click reaction between the aldehyde groups and aminooxy‐terminated PEG, leading to a structurally well‐defined star graft copolymer with arms consisting of poly(St‐co‐Ac) as backbone and PEG as side chains. Crystalline morphology and self‐assembly in water of the obtained star graft copolymer were also investigated. Opportunities are open for the star graft copolymer to form either multimolecular micelles or unimolecular micelles via control of the number of grafted PEG side chains. © 2013 Society of Chemical Industry     

Macro reversible addition–fragmentation chain transfer agent mixture as a means to enhance the electro‐optical performance of polymer‐dispersed liquid crystals

Macro reversible addition–fragmentation chain transfer (RAFT) agents, i.e. RAFT polystyrene (RAFT‐PS) and RAFT poly(n‐butyl acrylate) (RAFT‐PBA), were mixed. Polymer‐dispersed liquid crystals (PDLCs) were prepared using the mixture together with methyl acrylate and liquid crystal E7. The electro‐optical properties of the PDLCs obtained were investigated. The results showed that the advantages of the electro‐optical properties of RAFT‐PS‐ and RAFT‐PBA‐dependent PDLCs could be combined in RAFT agent mixture‐dependent PDLCs. Copyright © 2011 Society of Chemical Industry