Biodegradable and thermoresponsive micelles of triblock copolymers based on 2-(N,N-dimethylamino)ethyl methacrylate and ε-caprolactone for controlled drug delivery

Amphiphilic triblock copolymers, poly(2-(N,N-dimethylamino)ethyl methacrylate)_x-block-poly(caprolactone)-block-poly(2-(N,N-dimethylamino)ethyl methacrylate)_x, PDMAEMA_Co, were synthesized. Polymerization and structural features of the polymers were analyzed by different physicochemical techniques (GPC, ¹H NMR and FTIR). Formation of hydrophobic domains as cores of the micelles was studied by ¹H NMR and further confirmed by fluorescence. Dynamic light scattering measurements showed a monodispersed size distribution only for the copolymer with the lowest degree of polymerization, while increasing the length of PDMAEMA blocks leads to a bimodal size distribution. The micelles showed reversible dispersion/aggregation in response to temperature cycles through an outer polymer shell lower critical solution temperature (LCST) for PDMAEMA at temperatures between 54 and 87 °C. The triblock copolymer micelles were loaded with the sparingly water-soluble anticancer drug, chlorambucil, by a dialysis procedure. The drug release profile monitored by fluorescence showed that the release of chlorambucil from PDMAEMA nanoparticles is controlled by a combined degradation-diffusion mechanism.     

Synthesis and characterization of amphiphilic triblock polymers by copper mediated living radical polymerization

2-Dimethylaminoethyl methacrylate (DMAEMA) and 2-diethylaminoethyl methacrylate (DEAEMA) block copolymers have been synthesized by using poly(ethylene glycol), poly(tetrahydrofuran) (PTHF) and poly(ethylene butylenes) macroinitiators with copper mediated living radical polymerization. The use of difunctional macroinitiator gave ABA block copolymers with narrow polydispersities (PDI) and controlled number average molecular weights (M_n’s). By using DMAEMA, polymerizations proceed with excellent first order kinetics indicative of well-controlled living polymerization. Online ¹H NMR monitoring has been used to investigate the polymerization of DEAEMA. The first order kinetic plots for the polymerization of DEAMA showed two different rate regimes ascribed to an induction period which is not observed for DMAEMA. ABA triblock copolymers with DMAEMA as the A blocks and PTHF or PBD as B blocks leads to amphiphilic block copolymers with M_n’s between 22 and 24 K (PDI 1.24-1.32) which form aggregates/micelles in solution. The critical aggregation concentrations, as determined by pyrene fluorimetry, are 0.07 and 0.03 g dm⁻¹ for PTHF- and PBD-containing triblocks respectively.     

Self-initiated atom transfer radical polymerization of methyl methacrylate in cyclohexanone

The self-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in cyclohexanone (CHO) in the presence of CuCl₂/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) is reported. The linear semilogarithmic plot of ln([M]₀/[M]) vs time, the linear increase of number-average molecular weight (M_n) with conversion, and rather narrow molecular weight distributions (MWDs) have been observed, which are in agreement of the characteristics of living/controlled polymerization. The NMR spectrum revealed the existence of terminal chlorine. The chain extension further proved the living characteristic. The polymerization can only be successful using CHO as the solvent, and is well controlled at the temperature as low as 50 °C. The effects of ligand, solvent, temperature and monomer to catalyst ratio are all discussed.     

Synthesis of ABABA pentablock copolymers via copper mediated living radical polymerisation

In this work, the syntheses of poly(butyl methacrylate-b-methyl methacrylate-b-butyl methacrylate) triblock copolymer and poly(methyl methacrylate-b-butyl methacrylate-b-methyl methacrylate-b-butyl methacrylate-b-methyl methacrylate) pentablock copolymers using copper mediated living radical polymerisation are reported. Living radical polymerisations were performed using the system Cu^IBr/N-(n-propyl)-2-pyridylmethanimine as catalyst in conjunction with a difunctional initiator, the 1,4-(2^′-bromo-2^′-methylpropionoto)benzene (1). The syntheses of poly(MMA), poly(BMA-b-MMA-b-BMA) and poly(MMA-b-BMA-b-MMA-b-BMA-b-MMA) are described in detail using ¹H NMR spectroscopy and size exclusion chromatography. The living behaviour and the blocking efficiency of these polymerisations were investigated in each case. Difunctional initiator, 1, based on hydroquinone was synthesised and fully characterised and subsequently used to give difunctional poly(methyl methacrylate) macroinitiators with molecular weights up to 54,000 g mol⁻¹ and polydispersity between 1.07 and 1.32; molecular weights were close to the theoretical values. The difunctional macroinitiators were used to reinitiate butyl methacrylate to give triblock copolymers of M_n between 17,500 and 45,700 g mol⁻¹. Polydispersities remained narrow below 25,000 g mol⁻¹ but broadened at higher masses. The difunctional triblock macroinitiators were subsequently used to reinitiate methyl methacrylate to give ABABA pentablock copolymers with M_n up to 37,000 g mol⁻¹ with polydispersity=1.13. Under certain conditions radical-radical reaction led to a broadening of polydispersity index.     

A novel strategy for synthesis of amphiphilic π-shaped copolymers by RAFT polymerization

The amphiphilic π-shaped copolymers with narrow molecular weight distribution (M_w/M_n = 1.04-1.09) based on polystyrene (PSt) and poly(ethylene glycol) have been synthesized successfully. The reversible addition-fragmentation transfer (RAFT) polymerization of St in the presence of dibenzyl trithiocarbonate and N,N′-azobis(isobutyronitrile) (AIBN) yielded macro RAFT agent PSt-SC(S)S-PSt, subsequent reaction with excess maleic anhydride (MAh) at 80 °C in tetrahydrofuran afforded the PSt-MAh-SC(S)S-MAh-PSt. It was used as RAFT agent in the RAFT polymerization of St, and finally the amphiphilic π-shaped copolymers were obtained by the reaction of MAh with hydroxyl-terminated poly(ethylene glycol methyl ether) at 90 °C for 48 h. Their structures were confirmed by FT-IR and ¹H NMR spectra, and their molecular weight and molecular weight distribution were measured by gel permeation chromatography.     

Copper(I)-mediated radical polymerization of methacrylates in aqueous solution

α-Methoxypolyethylene oxide methacrylate was polymerized by copper(I)-mediated living radical polymerization in aqueous solution to give polymers with controlled number-average molecular masses and narrow polydispersities. When equimolar quantities of initiator with respect to copper(I) bromide were used, the reaction was extremely fast with quantitative conversion achieved in less than 5 min at ambient temperature. However, the molecular weight distribution was broad, and control over the number-average molecular weight (M_n) growth was extremely poor; this is ascribed to an increase in termination because of the increased rate as a result of the coordination of water at the copper center. The complex formed between copper(I) bromide and N-(n-propyl)-2-pyridylmethanimine, bis[N-(n-propyl)-2-pyridylmethanimine]copper(I), was demonstrated to be stable in aqueous solution by ¹H NMR over 10 h at 25 °C. However, on increasing the temperature to 50 °C, decomposition occurred rapidly. Thus, polymerization temperatures were maintained at ambient temperature. When longer alkyl chains were utilized in the ligand, that is, pentyl and octyl, the complex acted as a surfactant leading to heterogeneous solutions. When the catalyst concentration was reduced by two orders of magnitude, the rate of polymerization was reduced with 100% conversion achieved after 60 min with the M_n of the final product being higher than that predicted and the polydispersity equal to 1.43. Copper(II) was added as an inhibitor to circumvent these problems. When 10% of Cu(I) was replaced by Cu(II) {[Cu(I)] + [Cu(II)]/[I] = 1/100}, the mass distribution showed a bimodal distribution, and the rate of polymerization decreased significantly. With a catalyst composition [Cu(I)]/[Cu(II)] = 0.5/0.5 {[Cu(I)] + [Cu(II)]}/[I] = 1/100, polymerization proceeded slowly with 80% conversion reached after 22 h. Thus, the concentration of Cu(I) was further reduced with [Cu(I)]/[Cu(II)] = 10/90, {[Cu(I)] + [Cu(II)]}/[I] = 1/100. The system then contained [Initiator]/[Cu(I)] = 1000/1 and [I]/[Cu(II)] = 1000/9. Under these conditions, the reaction reached 50% after 5 h with the polymer having both an M_n close to the theoretical value and a narrow polydispersity of PDi = 1.15. Optimum results were obtained by increasing the amount of catalyst. When a ratio of [Cu(I)]/[Cu(II)] = 10/90 with a ratio of [Cu]/[I] = 1/1, a conversion of 100% was achieved after less than 20 h, leading to a product having M_n = 8500 and PDi = 1.15. Decreasing the amount of Cu(II) relative to Cu(I) to [Cu(I)]/[Cu(II)] = 0.5/0.5 (maintaining the overall amount of copper) led to 100% conversion after 75 min: M_n = 9500, PDi = 1.10. Block copolymers have been demonstrated by sequential monomer addition with excellent control over M_n and PDi. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1696–1707, 2001     

Synthesis, characterization and properties of a novel fluorinated methacrylate polymer

A fluorinated monomer of 2-(2,2,2-trifluoroethoxy)ethyl methacrylate (FEMA) was prepared by a “one pot” process and then a novel fluorinated methacrylate polymer, poly[2-(2,2,2-trifluoroethoxy)ethyl methacrylate] (PFEMA), was successfully synthesized via miniemulsion polymerization using cetyltrimethyl ammonium bromide (CTAB) as emulsifier, hexadecane (HD) as co-stabilizer and 2,2′-azobisisobutyronitrile (AIBN) as initiator. The chemical structure of PFEMA was characterized by FT-IR, ¹H NMR and ¹⁹F NMR. GPC results show that the number average molecular weight (M_n) of PFEMA was as high as 8.5 × 10⁵ g/mol and the polydispersity index (PDI) was only 1.3. SEM and DLS characterizations showed that the morphology of PFEMA latex was uniform spheres with the diameter of about 110–125 nm. It was also found that PFEMA has high thermo-stability (T_d > 200 °C), low glass transition temperature (T_g = 13.0 °C), and nice hydrophobicity (θ_water = 99.9°). Comparison studies on PFEMA and poly(2,2,2-trifluoroethyl methacrylate) show that an introduced functional group (–CH₂CH₂O–) has a significant effect on lowering T_g and improving hydrolysis resistance without impairing surface properties.     

Corrosion protection of iron surface modified by poly(methyl methacrylate) using surface-initiated atom transfer radical polymerization (SI-ATRP)

A new N-heterocyclic initiator N-[2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethyl]-2-bromoisobutyramide was synthesized and immobilized on the surface of iron. Methyl methacrylate was grafted from iron substrates via surface-initiated atom transfer radical polymerization (ATRP). The first-order kinetics of poly(methyl methacrylate) (PMMA) grafting from iron revealed the control of ATRP throughout the reaction, and the polymerization reached a high conversion producing polymers with good control of molecular weights (M _n?=?68,800) and low polydispersity indexes (M _w/M _n?<?1.32). The thickness of the polymer brush films was greater than 47 nm after 7 h of reaction time. The grafting density was estimated to be 0.48 chains?nm^?2. The iron surfaces at various stages of modification were characterized by scanning electron microscopy and energy dispersive spectrometer. The analytical results were consistent with a thin compact polymer coating on the surface of iron. Iron surface with grafted PMMA coating showed significant corrosion resistance. This work demonstrated that the surface-initiated ATRP is a versatile means of the surface modification of active metals with well-defined and functionalized polymer brushes.     

Tuning of the molecular packing structure of comb-shaped polymer-grafted silica by using surface-initiated ATRP to enhance the molecular-shape selectivity towards polycyclic aromatic hydrocarbons

Poly(octadecyl acrylate)-grafted silicas were prepared by surface-initiated atom transfer radical polymerization (ATRP). Initially, undecyl ester and allyl ester-based ATRP initiators were synthesized and then immobilized on silica. The surface-initiated ATRP of octadecyl acrylate was carried out from the initiator-grafted silicas using copper(I) bromide and N,N,N′,N′,N′′-pentamethyldiethylenetriamine as catalyst precursors to produce poly(octadecyl acrylate)-grafted silicas, Sil-C₁₁-ODA_n (obtained from undecyl ester) and Sil-C₃-ODA_n (originated from allyl ester), respectively. Both Sil-C₁₁-ODA_n and Sil-C₃-ODA_n were characterized by DRIFT, suspension-state ¹H NMR, solid-state ¹³C CP/MAS NMR spectroscopies, thermogravimetric analysis (TGA), elemental analysis and differential scanning calorimetry (DSC) measurements. Suspension-state ¹H NMR, solid-state ¹³C CP/MAS NMR and DSC analyses suggest that Sil-C₁₁-ODA_n demonstrated more ordered structure than Sil-C₃-ODA_n. In this paper, it is also described that for ordering of the polymer phase is accompanied by the selectivity increase for the separation of poly cyclic aromatic hydrocarbons (PAHs) in RP-HPLC.     

Synthesis of linear and starlike polymers from poly(propylene glycol) methacrylate using controlled radical polymerization

The copper‐catalyzed atom transfer radical polymerization (ATRP) of poly(propylene glycol) methacrylate (PPGM) in solution to produce linear and starlike polymers is reported, using methylethyl ketone as the solvent and a temperature of 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer without protecting hydroxyl end groups of monomer. The polymerizations were consistent with “living” or controlled processes, as revealed by the linear evolution of molecular weight with conversion. Increasing the [M]₀:[I]₀ ratio resulted in increasing molecular weights, whereas the polydispersity indices remained low (M_w/M_n < 1.4) even at high conversion. Decreasing the [CuBr]₀:[I]₀ ratio resulted in lower conversions, slightly larger polydispersities, and decreased molecular weights, likely resulting from a lower initiation efficiency. Polymers were characterized by ¹H and ¹³C NMR; molecular weights of polymers with low degrees of polymerization were estimated by end‐group analysis from ¹³C NMR spectra obtained using distortionless enhancement by polarization transfer and the gated decoupling techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 334–343, 2002     

Bacterial polyesters grafted with poly(ethylene glycol): Behaviour in aqueous media

An easy method for grafting of poly(3-hydroxyoctanoate-co-3-hydroxyundecenoate) (PHOU) was developed. Oxidation of the pendant double bonds of PHOU into carboxyl groups to yield poly(3-hydroxyoctanoate-co-3-hydroxy-9-carboxydecanoate) (PHOD) and the esterification of the carboxyl side groups with poly(ethylene glycol) (PEG) were carried out in a single reaction solution. The grafting yield is dependent on the molar mass of the PEG graft. The maximum carboxyl group conversion (52%) was obtained with PEG M_n = 350 and decreased with increasing molar mass of PEG (19% for PEG M_n = 2000). Yields were determined by ¹H and ¹³C NMR. Short PEG grafts lowered the glass transition temperature (PHOD-g-PEG 350 −57 °C) compared to PHOD (−19 °C) and PHOU (−39 °C). This effect depends on the COOH conversion and PEG chain length. Grafting enhanced the hydrophilic character of the modified polymers making them soluble in polar solvents, such as alcohols and water/acetone mixtures. PHOD-g-PEG films were more stable towards hydrolytic degradation as PHOD films. No obvious modification of films was observed after more than 200 days at pH 7.2 and 37 °C. The molar mass of the grafted polymers decreased only slightly during this period, while PHOD films were hydrolyzed into soluble fragments.     

Synthesis, characterization and degradability of the novel aliphatic polyester bearing pendant N-isopropylamide functional groups

The synthesis, characterization, and degradability of the novel aliphatic polyester bearing pendant N-isopropylamide functional group are reported for the first time. 2-(N-Isopropyl-2-carbamoylethyl)cyclohexanone (CCH) was first synthesized by the Michael reaction of N-isopropylacrylamide with cyclohexanone and was subsequently converted into 6-(N-isopropyl-2-carbamoylethyl)-?-caprolactone (CCL) by the Baeyer-Villiger oxidation reaction using 3-chloroperoxybenzoic acid (mCPBA) as the oxidant. Finally, the novel functionalized poly(?-caprolactone) bearing the pendant N-isopropylamide functional groups, poly(6-(N-isopropyl-2-carbamoylethyl)-?-caprolactone-co-?-caprolactone)s (poly(CCL-co-CL)), were carried out successfully by bulk ring-opening polymerization of CCL and ?-CL initiated by Sn(Oct)₂. Poly(CCL-co-CL) were characterized by ¹H NMR, ¹³C NMR, SEC and DSC. The copolymer containing 9.1 mol% CCL formed flexible films and was used to study its degradability. A phosphate buffer (pH = 7.4) with temperature 37 °C was adopted to proceed the degrading study all through. Compared with poly(?-caprolactone), the hydrolytic degradation of poly(CCL-co-CL) was much faster, which is confirmed by the weight loss and change of intrinsic viscosity.     

Synthesis of well-defined norbornenyl-terminated poly(alkyl methacrylate)s by group transfer polymerization and their grafting-through ring-opening metathesis polymerization

Highly efficient syntheses of poly(alkyl methacrylate)-based brush polymers were accomplished via a facile group transfer polymerization (GTP) and a consecutive grafting-through ring-opening metathesis polymerization. The GTP system, composed of the norbornenyl-methyl trimethylsilyl ketene acetal initiator and the N-(trimethylsilyl) bis(trifluoromethanesulfonyl)imide catalyst, rapidly and quantitatively generates norbornenyl-terminated poly(alkyl methacrylate) macromonomers with very narrow polydispersities (M_w/M_n < 1.10). The ring-opening metathesis polymerization of methacrylate macromonomers using Grubbs third generation catalyst successfully generated a group of methacrylate-based brush polymers, which assured the high quality of the macromonomers obtained from GTP.     

Controlled radical polymerization of methacrylates of various structures in the presence of the AIBN-FeCl3-N,N-dimethylformamide catalytic system

The controlled radical polymerization of methyl methacrylate, 2-ethoxyethyl methacrylate, and tert-butyl methacrylate conducted via atom-transfer radical polymerization in the presence of the AIBN-FeCl₃· 6H₂O-N,N-dimethylformamide catalytic system is studied. For all the systems under study, the rate of reaction is first order with respect to the monomer concentration. The number-average molecular mass of the polymers linearly increases with conversion, and their polydispersity indexes are below 1.6. The rate of polymerization decreases in the following sequence: 2-ethoxyethyl methacrylate > methyl methacrylate > tert-butyl methacrylate. The presence of ω-terminal chlorine atoms in polymer macromolecules is confirmed by ¹H NMR spectroscopy and through the block copolymerization of methyl methacrylate with a poly(ethoxyethyl methacrylate)-based macroinitiator.     

Aggregation and solubilization of organic solvents and petrol/gasoline in water mediated by block copolymers

A series of AB and ABA block copolymers of pDEGMEMA-b-pCHMA and pCHMA-b-pDEGMEMA-b-pCHMA cyclohexyl methacrylate (CHMA) and di(ethylene glycol) methyl ether methacrylate (DEGMEMA) with M_n ranging between 18,000 and 50,000 g mol⁻¹ and PDI = 1.09-1.32 were prepared via copper(I) mediated living radical polymerization with pyridylmethanimine ligands. Aggregation properties were investigated using a combination of ¹H NMR, dynamic and static light scattering. For comparative purposes poly(CHMA) and poly(DEGMEMA) homopolymers were prepared. The CAC values estimated for the di- and triblock copolymers soluble in cyclohexane are lower than 0.005 g L⁻¹ whereas the values found for block copolymers in methanol solutions are less than 0.070 g L⁻¹. DLS analysis showed the presence of micellar aggregates with diameters ranging from 25 to 40 nm with particle polydispersity indexes between 0.003 and 0.183. The pCHMA-b-pDEGMEMA-b-pCHMA micelles solubilized the aqueous phase in petrol/gasoline. The block copolymer-based micelles incorporate water within their hydrophilic domains, potentially overcoming a number of practical problems such as the formation of biphasic mixtures in solvent blends due to undesired water accumulation.     

A versatile synthesis of poly(lauryl acrylate) using N-(n-octyl)-2-pyridylmethanimine in copper mediated living radical polymerization

A facile synthesis of poly(lauryl acrylate) has been achieved by atom transfer radical polymerization using benzyl-2-bromoisobutyrate, copper (I) bromide, and N-(n-octyl)-2-pyridylmethanimine (OPMI). The latter was of great interest as its synthesis was very easy to carry out and as it allowed the reaction mixture to be homogeneous, which was essential for the control of the reaction. The polymerization was controlled under these conditions and was optimized with the addition of copper (II) bromide as deactivator. We proved that the synthesis of poly(lauryl acrylates) with well defined molecular weights and narrow polydispersities was possible using a ligand which does not require difficult synthesis and purification. We also showed the ability of pyridylmethanimine ligands to control ATRP of an acrylate derivative. Best results were obtained at 130 °C in xylene for [Initiator]₀/[Cu(I)Br]₀/[Cu(II)Br₂]₀/[OPMI]/[lauryl acrylate] equal to 1/1/0.05/2.2/181, respectively (M_n = 19,942, DPI = 1.28).     

Synthesis and Characterization of Four-Arm Star Poly(ϵ-caprolactone)-Block-Poly(cyclic-carbonate methacrylate) Copolymers by Combining Ring-Opening Polymerization With Atom Transfer Radical Polymerization

Well-defined four-arm star poly(?-caprolactone)-block-poly(cyclic carbonate methacrylate) (PCL-b-PCCMA) copolymers were synthesized by combining ring-opening polymerization (ROP) with atom transfer radical polymerization (ATRP). First, a four-arm poly(?-caprolactone) (PCL) macroinitiator [(PCL-Br)₄] was prepared by the ROP of ?-CL catalyzed by stannous octoate at 110°C in the presence of pentaerythritol as the tetrafunctional initiator followed by esterification with 2-bromoisobutyryl bromide. The sequential ATRP of CCMA monomer was carried out by using the (PCL-Br)₄ tetrafunctional macroinitiator (MI) and in the presence of CuBr/2, 2′-bipyridyl system in DMF at 80°C with [(MI)]:[CuBr]:[bipyridyl] = 1:1:3 to yield block polymers with controlled molecular weights (M_n (NMR) = 10700 to 27300 g/mol) by varying block lengths and with moderately narrow polydispersities (M_w/M_n = 1.2–1.4). Block copolymers with different PCL: PCCMA copolymer composition such as 50:50, 70:30 and 74:26 were prepared with good yields (48-74%). All these block copolymers were well characterized by NMR, FTIR and GPC and tested their thermal properties by DSC and TGA.     

Atom transfer radical polymerization of styrene initiated by triphenylmethyl chloride

Triphenylmethyl chloride (TPMCl) was employed for the first time as the initiator of atom transfer radical polymerization (ATRP) of styrene in the presence of CuCl/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) as catalyst and cyclohexanone as solvent. The kinetic plot was first-order with respect to monomer. A linear increase of number average molecular weight (M_n) vs. monomer conversion was observed, and the molecular weight distribution (MWD) was relatively narrow (M_w/M_n = 1.2-1.5). ¹H NMR spectra revealed the ω-Cl group at the chain end. Another two initiators, benzyl chloride (BzCl) and diphenylmethyl chloride (DPMCl), were also employed in contrast with triphenylmethyl chloride to investigate the influence of phenyl numbers on the polymerization.     

Study on the polymerizations of methyl methacrylate and styrene initiated with chlorotrimethylsilane and CuCl/N,N,N′,N″,N″-pentamethyldiethyltriamine

Methyl methacrylate (MMA) and styrene (St) have been radically polymerized in the presence of chlorotrimethylsilane and CuCl/N,N,N′,N″,N″-pentamethyldiethyltriamine (Me₃SiCl/CuCl/PMDETA). An analysis of the resultant polymers by ¹H NMR discloses terminal silyl group and chlorine atom in all the obtained polymers. Kinetics studies have been carried out by measuring monomer conversions and polymer molecular weights against polymerization time. The results indicate that, for both MMA and St polymerizations, the monomer conversions exhibit a quasi-linear relationship with polymerization time, and the polymer number-average molecular weight (M_n) also increases with monomer conversion. The molecular weights of both PS and PMMA exceed one hundred thousand. Regardless of molecular weight, all the polymers show narrow molecular distributions (M_w/M_n = 1.2-1.5). These polymerization reactions are speculated to follow a mechanism similar to that of atom transfer radical polymerization (ATRP).     

Reverse atom transfer radical polymerization of methyl methacrylate with FeCl3/pyromellitic acid

Iron^III chloride coordinated by pyromellitic acid was successfully used as the catalytic system in reverse atom transfer radical polymerization of MMA. Well-defined poly(methyl methacrylate) with narrow molecular weight distribution was synthesized in N,N-dimethylformamide at 80-110 °C. Chain extension was performed to confirm the living nature of the polymer. The presence of the end chloride atom on the resulting PMMA was demonstrated by ¹HNMR spectroscopy. This catalyst system is effective for reverse ATRP of methacrylates but not for acrylates.