Organic–inorganic composite materials as photoinitiator for controlling/living polymerization

Titanium dioxide (TiO₂)/graphitic carbon nitride (g‐C₃N₄) composites were first used as photoinitiator for photochemically mediated controlled/living polymerization of methyl methacrylate. The polymerization was successfully carried out in polyethylene glycol at room temperature with FeCl₃·6H₂O/N,N,N ′,N ′,N ″‐pentamethyldiethylenetriamine as complex catalyst and ethyl 2‐bromoisobutyrate as initiator in this case. A pseudo‐first‐order dependence of the monomer concentration on the polymerization time was observed. TiO₂/g‐C₃N₄ was verified to be an efficient photoinitiator. The polymerization was controlled to produce poly(methyl methacrylate) with narrow molecular weight distribution and controlled number average molecular weight (M_n,GPC). The M_n,GPC matched well with the theoretical values when using both UV and sunlight irradiation as light source. The effects of reaction conditions on the polymerization were investigated. The polymerization could be started and stopped through periodically switching on/off the light. The living nature was further supported by the chain extension experiments. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42891.     

Primary amine functionalized polystyrenes by atom transfer radical polymerization

Primary amine functionalized polystyrenes were prepared in quantitative yields by atom transfer radical polymerization using the adduct of 1‐(bromoethyl)benzene with 1‐(4‐aminophenyl)‐1‐phenylethylene as initiator for styrene polymerization in the presence of a copper(I) bromide/N,N,N′,N′,N″‐pentamethyldiethylenetriamine catalyst system. The polymerizations proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding primary amine functionalized polystyrenes with predictable molecular weights (M_n = 2 × 10³ to 10 × 10³ g mol^?1), relatively narrow molecular weight distributions (M_w/M_n = 1.03–1.49), well defined chain‐end functionalities and initiator efficiencies as high as 0.92. The polymerization process was monitored by gas chromatographic analysis. The primary amine functionalized polymers were characterized by thin layer chromatography, size exclusion chromatography, potentiometry and spectroscopy. Experimental results are consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative. Polymerization kinetic measurements show that the polymerization reaction follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases linearly with monomer conversion. © 2003 Society of Chemical Industry     

A water‐soluble CO2‐triggered viscosity‐responsive copolymer of N,N‐dimethylaminoethyl methacrylate and acrylamide

A series of copolymers PDAMs were synthesized with varying monomer ratio of acrylamide (AM) and N,N‐dimethylaminoethyl methacrylate (DMAEMA). The resulting copolymer solution shows an interesting property of viscosity‐response which is CO₂‐triggered and N₂‐enabled. Tertiary amine groups of PDAMs experience a reversible transition between hydrophobic and hydrophilic state upon CO₂ addition and its removal, which induced different rheological behavior. A combination of zeta‐potential, laser particle‐size analysis, and electrical conductivity analysis indicated that, when the monomer mole ratio of DMAEMA and AM is less than or equal to 3 : 7, the hydrophobic association structure between the copolymer molecules was destroyed by the leading of CO₂ and caused a viscosity decrease in its solution. On the contrary, when the monomer mole ratio of DMAEMA and AM is more than 3 : 7, a more extended conformation due to the protonated tertiary amine groups is formed and the enhanced repulsive interactions among the copolymer molecule results in a rise of its solution viscosity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40872.     

Use of a CO2‐switchable hydrophobic associating polymer to enhance viscosity–response

A series of copolymers, poly(acrylamide)‐co‐poly(N,N‐dimethylaminoethyl methacrylate)‐co‐poly(N‐cetyl DMAEMA) (abbreviation PDAMCn), was synthesized with different monomer ratios. The resulting copolymer solution shows pronounced viscosity–response property which is CO₂‐triggered and N₂‐enabled. Electrical conductivity experiment shows that tertiary amine group on DMAEMA experiences a protonate and deprotonate transition upon CO₂ addition and its removal. In addition, different incorporation rates of DMAEMA leads to two kinds of morphological change in the presence of CO₂ and thus induces different rheological behaviors. PDAMCn incorporating longer hydrophobic monomer (C₁₈DM) show more pronounced initial viscosity and higher critical stress required to cause network deformation, which consequently enhances the viscosity–response property of the solution. The addition of NaCl could also tune the viscosity of PDAMCn solution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41468.     

Synthesis and characterization of AB‐type copolymers poly(L‐lactide)‐block‐poly(methyl methacrylate) via a convenient route combining ROP and ATRP from a dual initiator

Diblock copolymers of poly(L ‐lactide)‐block‐poly(methyl methacrylate) (PLLA‐b‐PMMA) were synthesized through a sequential two‐step strategy, which combines ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP), using a bifunctional initiator, 2,2,2‐trichloroethanol. The trichloro‐terminated poly(L ‐lactide) (PLLA‐Cl) with high molecular weight (M_n,GPC = 1–12 × 10⁴ g/mol) was presynthesized through bulk ROP of L ‐lactide (L ‐LA), initiated by the hydroxyl group of the double‐headed initiator, with tin(II) octoate (Sn(Oct)₂) as catalyst. The second segment of the block copolymer was synthesized by the ATRP of methyl methacrylate (MMA), with PLLA‐Cl as macroinitiator and CuCl/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as catalyst, and dimethyl sulfoxide (DMSO) was chosen as reaction medium due to the poor solubility of the macroinitiator in conventional solvents at the reaction temperature. The trichloroethoxyl terminal group of the macroinitiator was confirmed by Fourier transform infrared spectroscopy (FTIR) and ¹H‐NMR spectroscopy. The comprehensive results from GPC, FTIR, ¹H‐NMR analysis indicate that diblock copolymers PLLA‐b‐PMMA (M_n,GPC = 5–13 × 10⁴ g/mol) with desired molecular composition were obtained by changing the molar ratio of monomer/initiator. DSC, XRD, and TG analyses establish that the crystallization of copolymers is inhibited with the introduction of PMMA segment, which will be beneficial to ameliorating the brittleness, and furthermore, to improving the thermal performance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of end‐functionalized poly(N‐isopropyl acrylamide) with zinc porphyrin and its photocatalytic activity under visible light

A series of well‐defined linear poly(N‐isopropyl acrylamide) with an asymmetrical zinc(II) porphyrin (ZnPor–PAM) end group was synthesized by atom transfer radical polymerization, wherein 5,10,15,20‐tetra(p‐bromopropanoyloxyethylphenyl) zinc porphyrin tripropionate was used as the initiator and CuBr/tris(2‐dimeoethyl)amine was used as the catalyst system. The structure of the ZnPor–PAM was characterized by Fourier transform infrared spectroscopy and ¹H‐NMR. In addition, the polydispersity index (PDI) obtained by gel permeation chromatography indicated that the molecular weight distribution was narrow; thus, the polymerization was well controlled (1.05 < PDI < 1.21). Because of the incorporation of hydrophobic porphyrin, the lower critical solution temperature of ZnPor–PAM was lower than that of the N‐isopropyl acrylamide homopolymer. Most interestingly, the ZnPor–PAM possessed remarkable photocatalytic activity for the oxidative degradation of methylene blue in the presence of hydrogen peroxide under visible‐light radiation. Moreover, ZnPor–PAM could be reused through the uncomplicated procedure, which exploited the thermoresponsive properties of ZnPor–PAM without any significant loss in activity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40523.     

A new atom transfer radical polymerization initiator based on phenolphthalein for the synthesis of bis‐allyloxy functionalized polystyrene macromonomers

A new atom transfer radical polymerization (ATRP) initiator, namely 2‐(1,1‐bis(4‐(allyloxy)phenyl)‐3‐oxoisoindolin‐2‐yl)ethyl 2‐bromo‐2‐methylpropanoate, was synthesized starting from phenolphthalein, a commercially available and an inexpensive chemical. Well‐ defined bis‐allyloxy functionalized polystyrene macromonomers (M_n,GPC 4800–11 700 g mol^?1) with controlled molecular weight and narrow molecular weight distribution (1.05–1.09) were synthesized using ATRP by varying the monomer to initiator feed ratio. The presence of allyloxy functionality on polystyrene was confirmed by Fourier transform infrared and ¹H NMR spectroscopy. A kinetic study of polymerization revealed pseudo‐first‐order kinetics with respect to monomer consumption. Initiator efficiency was found to be in the range 0.80–0.95. Matrix‐assisted laser desorption ionization time of flight spectra showed a narrow molecular weight distribution with control over the molecular weight. The reactivity of the allyloxy groups on polystyrene was successfully demonstrated by quantitative photochemical thiol‐ene click reaction with benzyl mercaptan as the model thiol reagent. Furthermore, the thiol‐ene click reaction was exploited to introduce other reactive functional groups such as hydroxyl and carboxyl by reaction of α,α′‐bis‐allyloxy functionalized polystyrene with 2‐mercaptoethanol and 3‐mercaptopropionic acid, respectively. © 2014 Society of Chemical Industry     

Photoinduced controlled/“living” polymerization of methyl methacrylate with flavone as photoinitiator

Photochemically mediated controlled/“living” polymerization of methyl methacrylate (MMA) triggered by flavone was studied. The polymerization was performed in ethanol at ambient temperature with CuBr₂/Tris(2‐dimethylaminoethyl)amine (Me₆TREN) as complex catalyst and ethyl 2‐bromoisobutyrate (EBiB) as initiator. The molar mass of poly(methyl methacrylate) (PMMA) was obtained and exhibited relatively narrow molecular weight distribution (M_w/M_n) which was characterized by gel permeation chromatography (GPC). Chain extension further indicated that the living nature was maintained in the photopolymerization system. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43845.     

Controlled radical polymerization catalyzed by CuCl/BDE complex in water medium. I. Polymerization of styrene and synthesis of poly(St‐b‐MMA)

The controlled radical polymerization of styrene in water medium, in the presence of polyoxyethylene nonyl phenyl ether, catalyzed and initiated by CuCl/BDE [bis(N,N′‐dimethylaminoethyl)ether]/R—X was studied. The results show that the molecular weight increased with conversion of the monomer. Using this controlled system, the block copolymer, poly(St‐b‐MMA), was successful synthesized in water medium. In reference to the system of CuCl/BDE/PhCH₂Cl, the polymerization may also occur in the micelle to produce a superhigh molecular mass (M_n = 1,500,000) polymer with monodispersion (MWD, M_w/M_n = 1.03). The Cu(I) and Cu(II) partition ratio in two phases, which may affect the reversible deactivation and debase the catalyst efficiency, was detected. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 802–807, 2000     

Fe‐mediated SET‐LRP of MMA and St in the presence of air

In this work, well‐defined homopolymers of methyl methacrylate (PMMA) and styrene (PSt) were prepared via single‐electron‐transfer living radical polymerization using CCl₄ as initiator and Fe(0)/N, N, N′,N′‐tetramethyl‐1,2‐ethanediamine as catalyst. The polymerization was conducted at 25 °C in N,N‐dimethylformamide in the presence of air. It proceeded in a ‘living’ manner, as indicated by the first‐order kinetics behavior, and the linear increase of the number‐average molecular weight (M_{n, GPC}) with conversion was close to the theoretical M_{n, theory}. Solvent and additives have a profound effect on the polymerization. In addition, the PMMA and PSt obtained remained of low dispersity. The chain‐end functionality of the obtained homopolymer of PMMA was characterized by proton nuclear magnetic resonance. A block copolymer of P(MMA‐block‐St) was achieved by using the obtained PMMA as macroinitiator. The living characteristics were further demonstrated by chain extension experiments. Copyright © 2012 Society of Chemical Industry     

Photomediated atom transfer radical polymerization of MMA under long-wavelength light irradiation

In this study, a novel photocatalyst, pentarylenebis(dicarboximide) dye: (1,6,13,18-tetra(4-(2,3,3-trimethylbut-2-yl)phenoxy)-N,N’-(2,6-diisopropylphenyl)-pentarylene-3,4,15,16-tetracarboxidiimide) (TTPDPT), was first used in metal-free photoinduced atom transfer radical polymerization (ATRP) of methyl methacrylates (MMA). The initiator was methyl α-bromoisobutyrate (MBI) and the light source was mild near-infrared (NIR) light irradiation (λ_max?≈?870 nm). The TTPDPT-mediated ATRP relies on in situ photoreduction of a MBI through an electron transfer process to generate the desired alkyl radical, which could induce polymerization of the monomer. The photoinduced metal-free ATRP of MMA shows typical characteristics of controlled free radical polymerization, showing the linear evolution of number-average molecular weight (M_n,GPC) with monomer conversion, where polymers with predetermined degree of polymerization have well-controlled molecular weights and narrow molecular weight distribution (M_w/M_n). The photoinduced metal-free ATRP of MMA can be carried out with just ppm level of TTPDPT. The polymerization initiation and propagation can be operated by the aid of pulsed light sequences while NIR light source was used to promote carbon–carbon bond formation and to produce poly(methyl methacrylate) (PMMA) with M_w/M_n as low as 1.5. The synthesized PMMA was characterized by ¹H nuclear magnetic resonance (¹H NMR). The resultant PMMA contained a bromide end group that can be employed to reinitiate styrene polymerization to produce block copolymers through chain extension experiments.     

Atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system

Atom transfer radical polymerization of n‐butyl methacrylate (BMA) was conducted in an aqueous dispersed system with different kinds of copper complexes. The partitioning behavior of the copper complexes, including CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipydine (dNbpy), CuCl₂/dNbpy, CuCl/2,2′‐bipydine (bpy), CuCl₂/bpy, CuCl/bis(N,N′‐dimethylaminoethyl)ether (bde), and CuCl₂/bde between the monomer (BMA), and water was studied in detail with ultraviolet‐visible spectroscopy. The results show that with a less hydrophobic ligand, such as bpy or bde, most of the Cu(I) or the Cu(II) complexes migrated from the BMA phase to the aqueous phase, the atom transfer equilibrium was destroyed, and the polymerization was nearly not controlled; it converted to classical emulsion polymerization. As to the very hydrophobic ligand dNbpy, although the partitioning study of the copper complexes indicated that not all the copper species were restricted to the organic phase, the linear correlation between the molecular weight and the monomer conversion and the narrow polydispersities confirmed that the polymerization was still quite well controlled. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3175–3179, 2003     

Synthesis,characterization, and curing of a new acrylate‐based dental restorative resin

The synthesis of monomer 1,3‐bis [(2‐hydroxy‐3‐acrylate) propyloxy]2‐hydroxy propane (BHAPP) is reported for the possible use in dental restoratives. The monomer was prepared by the reaction of acrylic acid with diglycerol diglycidyl ether (DGE) in the presence of triethyl amine as a catalyst. The progress of the reaction at 60°C followed by measuring the intensity of the epoxide absorption peak at 915 cm^?1 which has reached to its minimum value after 5 h. The structure of the monomer was characterized by FTIR and ¹H‐NMR. The monomer was a moderately viscous light yellow color liquid having a refractive index of 1.544. Thermal curing of the monomer in DSC in the presence of benzoyl peroxide showed exothermic peak with maximum temperature (T_p) varied from 89 to 107°C depending on the heating rate and activation energy of 83 kJ/mol. Photopolymerization of the monomer by visible light in the presence of camphorquinone and N,N‐dimethylaminoethyl methacrylate as the photoinitiating system showed maximum 60% conversion after 40 s exposure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) by ATRP using a fluorescein-based initiator

Summary A new fluorescent initiator fluorescein 2-bromoisobutyrate (Flu-Br) was synthesized. The use of Flu-Br as initiator, Me₆TREN as ligand and CuCl as catalyst by atom transfer radical polymerization allowed for chain-end fluoresceined poly(N-isopropylacrylamide) (Flu-PNIPAM) in one step. The polymerization reached high conversion (65%) and low polydispersity (PDI) (1.15∼1.28). The linearity plot of the M_n,GPC and M_n,NMR against conversion and the low PDI revealed the well-controlled polymerization by ATRP. In addition, N-isopropylacrylamide (NIPAM) was copolymerized with hydrophilic N,N-dimethylacrylamide (DMAM) using Flu-Br initiator by ATRP. By changing the feed ratio of NIPAM to DMAM, it was very easy to obtain thermo-sensitive fluorescent copolymers with proper lower critical solution temperature (36.0±0.2 °C, 38.0±0.2 °C). The pH dependence on fluorescence intensity of Flu-PNIPAM displayed a similar behavior to the parent fluorescein.     

Rapid ambient temperature atom transfer radical polymerization of tert‐butyl acrylate

BACKGROUND: Atom transfer radical polymerization (ATRP) is considered to be one of the better and easier synthetic tools for the preparation of polymers with controlled molecular weights and polydispersities. Ambient temperature ATRP of tert‐butyl acrylate (tBA) was studied in a detailed manner with ethyl 2‐bromoisobutyrate (EBrB) and tert‐butyl 2‐bromoisobutyrate (tBuBrB) as the initiators for three different degrees of polymerization. RESULTS: Details pertaining to the kinetics of polymerization using different initiators are reported. It is observed that dimethylsulfoxide accelerates the polymerization at room temperature. The use of Cu(II) as the deactivator produces very narrow dispersity polymers. A diblock copolymer, poly(tert‐butyl acrylate)‐block‐poly(methyl methacrylate), was synthesized from the poly(tBA) macroinitiator demonstrating the controlled living nature of the polymerizations. CONCLUSIONS: The rate of polymerization is more rapid with a secondary initiator (ethyl 2‐bromopropionate) compared to the tertiary initiators EBrB and tBuBrB. From the detailed kinetic results it is observed that tris(2‐dimethylaminoethyl)amine was a better ligand compared to tris(2‐aminoethyl)amine in terms of achieving controlled polymerization. Copyright © 2007 Society of Chemical Industry     

Synthesis and characterization of amphiphilic block copolymers of methyl methacrylate with poly(ethylene oxide) macroinitiators formed by atom transfer radical polymerization

Amphiphilic ABA triblock copolymers of poly(ethylene oxide) (PEO) with methyl methacrylate (MMA) were prepared by atom transfer radical polymerization in bulk and in various solvents with a difunctional PEO macroinitiator and a Cu(I)X/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalyst system at 85°C where X=Cl or Br. The polymerization proceeded via controlled/living process, and the molecular weights of the obtained block copolymers increased linearly with monomer conversion. In the process, the polydispersity decreased and finally reached a value of less than 1.3. The polymerization followed first‐order kinetics with respect to monomer concentration, and increases in the ethylene oxide repeating units or chain length in the macroinitiator decreased the rate of polymerization. The rate of polymerization of MMA with the PEO chloro macroinitiator and CuCl proceeded at approximately half the rate of bromo analogs. A faster rate of polymerization and controlled molecular weights with lower polydispersities were observed in bulk polymerization compared with polar and nonpolar solvent systems. In the bulk polymerization, the number‐average molecular weight by gel permeation chromatography (M_n,GPC) values were very close to the theoretical line, whereas lower than the theoretical line were observed in solution polymerizations. The macroinitiator and their block copolymers were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry, thermogravimetry (TG)/differential thermal analysis (DTA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). TG/DTA studies of the homo and block copolymers showed two‐step and multistep decomposition patterns. The DSC thermograms exhibited two glass‐transition temperatures at ?17.7 and 92°C for the PEO and poly(methyl methacrylate) (PMMA) blocks, respectively, which indicated that microphase separation between the PEO and PMMA domains. SEM studies indicated a fine dispersion of PEO in the PMMA matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 989–1000, 2005     

Structural estimation of particle arrays at air–water interface based on silica particles with well‐defined and highly grafted poly(methyl methacrylate)

Silica nanoparticles with well‐defined, highly grafted dense poly(methyl methacrylate) (MMA) were prepared by surface‐initiated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) of methyl methacrylate with an initiator‐fixed silica particle in the presence of air. Two different polymerizations of MMA were carried out under the same conditions using tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) and N,N,N′,N′,N″‐pentamethyldiethylene‐triamine (PMDETA) as the ligand, respectively. In the CuCl₂/PMDETA system, polymerization appeared to be more controlled with a lower polydisperisty compared with the CuCl₂/Me₆TREN system. The monolayer of these particles was formed at the air–water interface using Langmuir‐Blodgett (LB) technique. Multilayers of the particles were fabricated by repetition of LB depositing. A surface pressure–area (π–A) measurement and SEM observation were used to characterize the particle arrays. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Monomers for adhesive polymers, 8a crosslinking polymerization of selected N‐substituted bis(acrylamide)s for dental filling materials

The free‐radical polymerization of bis‐(N‐ethylacrylamido)‐ethylenglycol ( I ), N,N′‐dimethyl‐1,6‐bis (acrylamido)‐hexan ( II ), and N,N′‐diethyl‐1,3‐bis(acrylamido)‐propan ( III ) were investigated. The cross‐linking polymerization was followed in bulk by using the ampoules technique and gravimetry. Polymerizations exhibited an abnormal kinetic behavior. For the monomer II , for example, the reaction order to 2,2′‐ azobisisobutyronitril (AIBN) initiator of 1.28, and the polymerization overall activation energy of 151 kJ/mol between 50 and 75°C were determined. The increasing temperature and decreasing initiator concentration resulted in an increase of double bonds consumption in the formed polymer network. At 75°C the residual unsaturation was under 2%, compared with 9.9% at 50°C. The monomer conversion‐time dependences were complemented also with differential scanning calorimetry (DSC) recording the heat released during polymerization. The extension of peak time with decreasing the instant heat flow rate at this point sort the studied bis(acrylamide)s according the reactivity in the following sequence: monomer III > I > II . The polymer samples sol–gel analyses in ethanol allowed the determination of the molecular weight M_c between the network crosslinks. The presence of microgel particles at the very beginning of polymerization and the changes in chain conformation with temperature we consider as the way in which was affected the polymerization kinetics of these monomers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Kinetic study of the atom transfer radical polymerization of n‐docosyl acrylate

The atom transfer radical polymerization (ATRP) of n‐docosyl acrylate (DA) was studied at 80°C in N,N‐dimethylformamide using the carbon tetrabromide/FeCl₃/2,2′‐bipyridine (bpy) initiator system in the presence of 2,2′‐azobisisobutyronitrile (AIBN) as the source of reducing agent. The rate of polymerization exhibits first‐order kinetics with respect to the monomer. The linear relationship between the molecular weight of the resulting poly(n‐docosyl acrylate) with conversion and the narrow polydispersity of the polymers indicates the living characteristics of the polymerization reaction. The significant effect of AIBN on the ATRP of DA was studied keeping [FeCl₃]/[bpy] constant. A probable reaction mechanism for the polymerization system is postulated to explain the observed results. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2147–2154, 2005