Well-defined poly(methyl methacrylate) grafted to polyethylene with reverse atom transfer radical polymerization initiated by peroxides

A reverse atom transfer radical polymerization (ATRP) with FeCl₃/PPh₃/peroxides was applied to grafting of methyl methacrylate (MMA) to polyethylene (PE). Peroxides on PE were generated by γ-ray irradiation in air. A reverse ATRP of methyl methacrylate with benzoyl peroxide, cumene hydroperoxide, and di-t-butyl peroxide as models of the PE peroxides was confirmed to proceed successfully in living fashion. In an inhomogeneous (bulk) grafting system, the grafting ratio (GR) of PMMA to PE weights, molecular weight (M_n) and its distribution of grafted PMMA were not controlled with time, i.e. the grafting of MMA with a reverse ATRP to the oxidized PE failed in well-defined grafting. On the other hand, a homogeneous (in o-xylene solution) grafting system provided a well-controlled M_n, narrow polydispersity of grafted PMMA and a linear relation between M_n and GR, indicating a controlled grafting. The controlled grafting with a reverse ATRP combined to a radiation-induced grafting was achieved successfully. The grafting of MMA to polypropylene in this way also seemed to be controlled well.     

A novel route for the synthesis of poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) grafted titania nanoparticles via ATRP

A new method is presented for grafting poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (P(HEMA-co-MMA)) chains from the surface of TiO₂ nanoparticles via atom transfer radical polymerization (ATRP). First, the ATRP initiators were immobilized onto the TiO₂ surface by using 3-aminopropyltriethoxysilane coupling agent and 2-bromoisobutyryl bromide. Then the copolymerization of 2-hydroxyethyl methacrylate with methyl methacrylate was initiated and propagated on the TiO₂ surface by ATRP. The resulting composite nanoparticles were characterized by means of XPS, FT-IR, ¹H NMR, GPC and TGA. The results indicated that the grafting of copolymer chains from the TiO₂ surface was successful. This method opens up new avenues for the preparation of TiO₂-polymer nanocomposites.     

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.     

Well-defined dibenzocyclooctyne end functionalized polymers from atom transfer radical polymerization

The dibenzocyclooctyne end functionalized agent 1 was designed as atom transfer radical polymerization (ATRP) initiator. The ATRP was then explored on three types of monomers widely used in free radical polymerization: methyl methacrylate, styrene, and acrylates (n-butyl acrylate and tert-butyl acrylate). The living polymerization behaviors were obtained for the methyl methacrylate and styrene monomers. The SPAAC click reactivity of dibenzocyclooctyne end group were demonstrated by successfully reacting with azide functionalized small chemical agents and polymers. Various topological polymers such as block and brush polymers were produced from strain-promoted azide-alkyne cycloaddition reaction (SPAAC) using the resultant dibenzocyclooctyne end functionalized poly(methyl methacrylate)/polystyrene as building blocks. For the acrylates, however, the polymerization did not hold the living characteristics with the dibenzocyclooctyne end functionalized ATRP initiator 1.     

Preparation of Ni-g-polymer core–shell nanoparticles by surface-initiated atom transfer radical polymerization

Surface-initiated atom transfer radical polymerization (si-ATRP) technique was successfully employed to modify Ni nanoparticles with polymer shells. ATRP initiators were covalently bonded onto Ni nanoparticle surfaces by a combination of ligand exchange and condensation reactions. Various kinds of polymers including poly(methyl methacrylate) (PMMA) and poly(n-isopropylacrylamide) (PNIPAM) were grafted from the immobilized initiators. The grated polymer shells gave Ni nanoparticles exceptionally good dispersion and stability in solvents. Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and transmission electron spectroscopy (TEM) were employed to confirm the grafting and to characterize the nanoparticle core–shell structure. Gel permeation chromatography (GPC) studies of cleaved polymer chains revealed that the grafting polymerization was well controlled. The magnetic properties of Ni-g-polymer nanoparticles were also studied.     

Surface grafting of polymers onto aramid powder: graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface of aramid powder

The radical graft polymerization of vinyl monomers onto the surface of aramid powder, i.e., poly(p-phenylene terephthalamide) powder, initiated by azo groups introduced onto the surface was investigated. The introduction of azo groups onto the aramid surface was achieved by the reaction of surface acyl chloride groups, which were introduced by the treatment of aramid powder with adipoyl dichloride, with 2,2′-azobis[2-(2-imidazolyn-2-yl)propane] in the presence of pyridine: the amount of azo groups thus introduced onto the surface was determined to be 0.57 mmol/g by elemental analysis. It was found that the polymerizations of methyl methacrylate (MMA) and styrene were successfully initiated by the azo groups on the surface and that the corresponding polymers were grafted onto the surface. The percentage of surface grafting of polystyrene and poly(methyl methacrylate) (PMMA) increased up to 37.6 and 26.5%, respectively. Thermogravimetric analysis of polymer surface-grafted aramid powder confirmed that the grafting of polymers is limited on the surface. The polymerization rate was found to bear a first-order dependence on the concentration of aramid powder having azo groups. This suggests that in graft polymerization, unimolecular termination preferentially proceeds.     

二醋酸纤维素接枝聚甲基丙烯酸甲酯的合成与表征

以二醋酸纤维素（CDA）为接枝骨架,利用原子转移自由基聚合(ATRP)技术接枝聚甲基丙烯酸甲酯(PMMA),合成接枝共聚物(CDA-g-PMMA),采用FT-IR、1H-NMR、DSC、XRD和GPC等方法表征了CDA-g-PMMA的结构与物化性能,结果显示,支链PMMA的引入,降低了材料的熔融温度和结晶度,另外还增加了材料的韧性,ATRP方法有效的控制了共聚物相对分子质量分布系数。     

Photo-induced ATRP of MMA without ligands in ionic liquid

Fe-mediated photo-induced atom transfer radical polymerization (ATRP) of methyl methacrylate was studied with chlorophyll A as photoredox catalyst in the absence of ligands. This is the first report on photo-induced and FeBr₃-mediated ATRP. A low-cost and environmentally friendly ATRP is provided in this system. A good linear semi-logarithmic plot of polymerization kinetics is the first-order time conversion, and narrow molecular weight distributions explain the well-controlled behavior. The measured number average molecular weight, M _n,GPC (determined by gel permeation chromatography), is increased with monomer conversion, and it is in good agreement with the theoretical values (M _n,th). The effect of FeBr₃ is studied with respect to the polymerization. The values of the resultant PMMA increased with reduced FeBr₃ concentration. In this system, the effect of periodic light/off process has been investigated through chain growth instantly turned on and off in response to the visible light. The polymerization was controllable even though the concentration of Fe-based catalyst was dropped to 4 ppm. The chain-end group having a functionality in the synthesized poly(methyl methacrylate) was characterized by nuclear magnetic resonance spectrometry (¹H NMR). However, chain extension experiments show reserved chain-end functionality in the synthesized polymers and further confirm the “living” feature of the Fe-mediated photo-induced atom transfer radical polymerization.     

Grafting of vinyl polymers onto VGCF surface and the electric properties of the polymer-grafted VGCF

The graft polymerization of vinyl monomers onto vapor grown carbon fibers (VGCF) initiated by the system consisting of molybdenum hexacarbonyl (Mo(CO)₆) and trichloroacetyl (COCCl₃) groups introduced onto the surface was investigated. The introduction of trichloroacetyl groups onto VGCF surface was successfully achieved by the reaction of carboxyl groups on VGCF surface with trichloroacetyl isocyanate. It was found that the radical graft polymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and glycidyl methacrylate (GMA) is successfully initiated by the system consisting of Mo(CO)₆ and COCCl₃ groups introduced onto the surfaces. In the polymerization, the corresponding vinyl polymers were effectively grafted onto the VGCF surface, based on the propagation of polymer from surface radicals formed by the interaction of trichloroacetyl groups and Mo(CO)₆: the percentage of PMMA grafting reached 40%. Polymer-grafted VGCF gave a stable colloidal dispersion in good solvents for grafted polymer. The electric resistance of composite prepared from the polymer-grafted VGCF suddenly increased in organic solvent vapor over 10³ times, and returned to initial resistance when it was transferred into dry air. These results indicate that such composites can be used as novel gas sensors.     

Photo‐Induced atom transfer radical polymerization with nanosized α‐Fe2O3 as photoinitiator

Photo‐induced atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was achieved in poly(ethylene glycol)‐400 with nanosized α‐Fe₂O₃ as photoinitiator. Well‐defined poly(methyl methacrylate) (PMMA) was synthesized in conjunction with ethyl 2‐bromoisobutyrate (EBiB) as ATRP initiator and FeCl₃·6H₂O/Triphenylphosphine (PPh₃) as complex catalyst. The photo‐induced polymerization of MMA proceeded in a controlled/living fashion. The polymerization followed first‐order kinetics. The obtained PMMA had moderately controlled number‐average molecular weights in accordance with the theoretical number‐average molecular weights, as well as narrow molecular weight distributions (M_w/M_n). In addition, the polymerization could be well controlled by periodic light‐on–off processes. The resulting PMMA was characterized by ¹H nuclear magnetic resonance and gel permeation chromatography. The brominated PMMA was used further as macroinitiator in the chain‐extension with MMA to verify the living nature of photo‐induced ATRP of MMA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42389.     

Influence of chemical functionalization of carbon nanotubes on their dispersibility in alkyl methacrylate polymer matrix

Nanocomposites based on poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate‐co‐octadecyl methacrylate) (M/O) matrices and four different types of multiwall carbon nanotubes: pristine, oxidized (MWCNT–COOH), methyl ester (MWCNT–COOCH₃), and dodecyl ester (MWCNT–COOC₁₂H₂₅) functionalized, were prepared in situ by radical (co)polymerization. The effectiveness of preparation of nanocomposites regarding dispersion and distribution of various MWCNT in polymer matrices was sized by Scanning electron microscopy. In case of PMMA matrix, the best dispersion and distribution were accomplished for MWCNT–COOCH₃ due to their chemical resemblance with polymer matrix. After the introduction of 10 mol % of octadecyl methacrylate in polymer matrix a fairly good dispersion and distribution of MWCNT–COOCH₃ were retained. The addition of 1 wt % of MWCNTs caused a significant reduction in the degree of polymerization of the PMMA matrix. But at the same time, the present MWCNTs increased storage modulus of PMMA nanocomposites except for dodecyl ester functionalized MWCNT. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46113.     

N-[Salicylidene-1,2-ethanediaminoethyl]-2-bromoisobutyramide as initiator for atom transfer radical polymerization and surface-initiated ATRP of methyl methacrylate on copper

N-[Salicylidene-1,2-ethanediaminoethyl]-2-bromoisobutyramide (SEB) was synthesized and characterized by elemental analysis, FT-IR and ¹H NMR. It had been successfully used as a bidentate initiator for the atom transfer radical polymerization (ATRP) of methyl methacrylate with CuBr/2,2′-bipyridine as the catalyst and N,N-dimethylformamide as the solvent at 70 °C. The kinetics was first order in monomer and the number-average molecular weight of the polymer increased linearly with monomer conversion, indicating the ‘living’/controlled nature of the polymerization. The polymerization reached high conversions producing polymers with a low molecular weight distribution (M _w/M _n = 1.34). The obtained poly(methylmethacrylate) (PMMA) functionalized with salicylidene-1,2-ethanediaminoethyl and ω-Br as the end groups were characterized by FT-IR spectroscopy. They can be used as macroinitiators for chain-extension reaction. Then, PMMA coatings were grafted from copper substrates by surface-initiated ATRP from a surface-bound SEB initiator. The electrochemical impedance spectroscopy measurements and potentiodynamic electrochemical experiments confirmed the successful grafting of the polymer coatings. Greatly improved short-term anticorrosive properties for PMMA modified electrodes were demonstrated by substantially increased resistance of the film for a period of 24 h as compared to bare copper.     

Poly(methyl methacrylate) nanocomposites based on graphene oxide: a comparative investigation of the effects of surface chemistry on properties and foaming behavior

The effects of oxygen functional groups and alkyl chains at the surface of graphene oxide (GO) on the thermal stability, mechanical properties and foaming behavior of poly(methyl methacrylate) (PMMA) nanocomposites were investigated. Alkyl‐functionalized GO (GO‐ODA) was prepared by grafting octadecylamine (ODA) on the surface of GO. PMMA/GO and PMMA/GO‐ODA nanocomposite were obtained by solution blending and were foamed using supercritical carbon dioxide (scCO₂). GO‐ODA, with the presence of alkyl chains, showed a better dispersion capability in PMMA matrix than GO with a large amount of oxygen functional groups. In addition, the good dispersion capability increased thermal stability and mechanical strength. In comparison with PMMA/GO samples foamed at 70 °C, PMMA/GO‐ODA nanocomposite foams displayed improved cell structures with higher cell density, smaller cell size and more homogeneous cell size distribution, which results from the strong heterogeneous nucleation due to alkyl chains on the GO surface. The foaming behaviors became more complicated at 80 °C as the GO might be intercalated and exfoliated with the aid of scCO₂, thus further enhancing the heterogeneous nucleation during the foaming process. The results indicated that the surface chemistry of GO was closely related to the properties and foaming behavior of the nanocomposites. © 2016 Society of Chemical Industry     

Direct grafting poly(methyl methacrylate) from TiO2 nanoparticles via Cu2+‐amine redox‐initiated radical polymerization: An advantage of monocenter initiation

Cu²⁺ can oxidize amines to generate radicals to initiate radical polymerization of electron‐deficient monomers under mild conditions. Here, CuSO₄‐catalyzed redox‐initiated radical polymerizations of methyl methacrylate from amino‐functionalized TiO₂ nanoparticles (TiO₂‐NH₂ nanoparticles) was performed to prepare TiO₂ nanoparticles grafted with poly(methyl methacrylate) (TiO₂‐g‐PMMA hybrid nanoparticles) in dimethylsulfoxide or N,N‐dimethylformamide at 90°C. Infrared spectroscopy, thermogravimetric analysis, and X‐ray photoelectron spectroscopy confirmed the presence of the grafted PMMA and the grafting yield was about 50 wt%. Microscopy and particle‐size analysis indicated that TiO₂‐g‐PMMA nanoparticles had a good affinity to organic media. Because only aminyl radical (? NH?) on TiO₂ nanoparticles formed in Cu²⁺‐amine redox‐initiation step, there was no free PMMA chains formed during polymerization. Thus, our protocol provides a facile strategy to prepare inorganic/organic hybrid nanoparticles via one‐pot Cu²⁺‐amine redox‐initiated free radical polymerization. POLYM. ENG. SCI., 55:735–744, 2015. © 2014 Society of Plastics Engineers     

Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) of MMA from PANI Powders

Summary The macro-initiator for atom transfer radical polymerization (ATRP), bromoacetyl modified polyaniline (BrA-PANI) with a bromoacetyl group content of 0.27 m mol/g, was successfully prepared by the bromoacetylation of the amine groups of the undoped PANI with bromoacetylbromide. Then the poly(methyl methacrylate) (PMMA) brushes were grafted from the BrA-PANI surface via a surface-initiated atom transfer radical polymerization (SI-ATRP) of MMA with the catalysts of 1,10-phenanthroline and Cu(I)Br. The percentage of grafting (PG%) was found to increase linearly with the increasing of the polymerizing time and that of 27.18% was achieved after the SI-ATRP in toluene solution at 80 °C for 6 h. The product, the shell-core poly(methyl methacrylate)-polyaniline (PMMA-PANI) powders were also characterized by FT-IR, XPS and SEM.     

Physical and mechanical properties of poly(methyl methacrylate) -functionalized graphene/poly(vinylidine fluoride) nanocomposites: Piezoelectric β polymorph formation

Poly(methyl methacrylate) -functionalized graphene (MG) is prepared from graphene oxide (GO), using atom transfer radical polymerization (ATRP) and reducing with hydrazine hydrate. PMMA causes an increase of height of MG sheet for polymerization of MMA at side and basal planes. MG layers become thinner for exfoliation during composite formation. Graphene sheets enhance piezoelectric β-polymorph PVDF formation. MG sheets nucleate PVDF crystals and a gradual decrease of α phase occurs with a concomitant rise of β phase. Thermal stability of nanocomposites increases significantly and the T_g increase is really large (21 °C). Storage modulus shows an increase of 124%, stress at break 157% and Young’s modulus 321% for 5% MG. Parallel orientation of graphene sheets changes to random orientation for high graphene content. It exhibits conducting percolation threshold at 3.8% MG and variable range hopping model suggests that conductivity is contributed from the intergrain tunnelling and hopping between the grains.     

Controlled grafting of polymer brushes on poly(vinylidene fluoride) films by surface‐initiated atom transfer radical polymerization

Controlled grafting of well‐defined polymer brushes on the poly(vinylidene fluoride) (PVDF) films was carried out by the surface‐initiated atom transfer radical polymerization (ATRP). Surface‐initiators were immobilized on the PVDF films by surface hydroxylation and esterification of the hydroxyl groups covalently linked to the surface with 2‐bromoisobutyrate bromide. Homopolymer brushes of methyl methacrylate (MMA) and poly(ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the α‐bromoester‐functionalized PVDF surface. The chemical composition of the graft‐functionalized PVDF surfaces was characterized by X‐ray photoelectron spectroscopy (XPS) and attenuated total reflectance (ATR)–FTIR spectroscopy. Kinetics study revealed a linear increase in the graft concentration of PMMA and PEGMA with the reaction time, indicating that the chain growth from the surface was consistent with a “controlled” or “living” process. The “living” chain ends were used as the macroinitiator for the synthesis of diblock copolymer brushes. Water contact angles on PVDF films were reduced by surface grafting of PEGMA and MMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3704–3712, 2006     

Synthesis of NR‐g‐PMMA by “grafting from” method using ATRP process

Grafting poly(methyl methacrylate) or PMMA from natural rubber (NR) using ATRP process, NR has to be transformed into bromoalkyl‐functionalized NR (NRBr) acting as ATRP macroinitiator. The NRBr was prepared by two‐step chemical modification i.e., epoxidation and epoxide ring opening reaction using a nucleophile containing bromine atom such as 2‐bromopropionic acid ( A1 ) and 2‐bromo‐2‐methylpropionic acid ( A2 ). The fixation of A1 and A2 on 4‐methyl‐4‐octene, a model representing one repeat unit of NR, modified by epoxidation was prior studied and it was found that the resulting addition products from A2 using as ATRP initiator for MMA gave a better control of M _n,exp and low PDI of PMMA than that from A1 . Then, the NR was transformed into ATRP rubber macroinitiator via epoxidation, followed by epoxide ring addition with only A2 . ¹H NMR was employed to determine the amount of A2 addition units on NR, which is considered to be the same amount of grafting sites for ATRP of MMA. The grafting of PMMA was then successfully carried out from the NR backbone by ATRP process. The PMMA grafts of the NR‐g‐PMMA were indeed linked to the NR backbone via ester linkage of the A2 unit. The PMMA grafts could be cleaved from the NR backbone by acid hydrolysis, while PMMA grafting by other conventional radical reaction could not be done. Then, the average MW of PMMA grafts after separation using acetone extraction was evaluated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Friction spot welding of PMMA with PMMA/silica and PMMA/silica-g-PMMA nanocomposites functionalized via ATRP

In the present study, the feasibility of Friction Spot Welding (FSpW) of a commercial-grade poly(methyl methacrylate) (PMMA) (PMMA GS) and PMMA 6N/functionalized silica (SiO₂) nanocomposites was investigated. The silica nanoparticles were functionalized via atom transfer radical polymerization (ATRP) with PMMA chains to achieve a uniform dispersion in the polymer matrix. The successful functionalization of silica nanoparticles with PMMA chains via ATRP was evaluated by ATR-FT-IR and TGA measurements. Rheological investigations of the silica nanocomposites showed a plateau of the storage modulus G′ at low frequencies (0.01–0.03 rad/s) as a result of elastic particle–particle interactions. Overlap friction spot welds consisting of PMMA GS and a 2 wt% SiO₂-g-PMMA nanocomposite were successfully prepared and compared to spot joints of PMMA GS welded with PMMA 6N and PMMA 6N/silica nanocomposite with 2 wt% unfunctionalized silica nanoparticles. Raman mappings of selected areas of cross-sectional plastographic specimens revealed an increased mixing behavior between the two polymer plates in the case of PMMA GS/2 wt% SiO₂-g-PMMA joints. Although the joints welded with PMMA 6N/silica nanocomposites showed a reduction of 22% in lap shear strength and 21% displacement at peak load compared with the neat PMMA spot welds, they can compete with other state-of-the-art PMMA welding techniques such as thermal bonding and ultrasonic welding, which indicates the potential of friction spot welding as an alternative fabrication technology for joining future nanocomposite engineering parts.     

Structural characterization,thermal properties,and density functional theory studies of PMMA‐maghemite hybrid material

Maghemite (γ‐Fe₂O₃)‐poly(methyl methacrylate) (PMMA) nanocomposites were prepared by grafting 3‐(trimethoxy‐silyl) propyl methacrylate on the surface of maghemite nanoparticles, this process being followed by methyl methacrylate radical polymerization. Three different hybrids with 0.1, 0.5, and 2.5 wt% of maghemite nanoparticles were studied. The results indicate that these nanocomposites consist of a homogeneous PMMA matrix in which maghemite nanoparticles with a bimodal size distribution are embedded. The existence of covalent bonding between silane monomers and atoms on the maghemite surface was evidenced. AFM images showed a clear increase in surface roughness for increasing maghemite content. The thermal stability of PMMA‐maghemite nanocomposites is higher than that of pure PMMA and increases for increasing maghemite content. The results of our theoretical studies indicate that the electron density in the maghemite nanoparticle is not homogenous, the low electron density volumes being supposed to be radical trappers during PMMA decomposition, thus acting as a thermal stabilizer. POLYM. COMPOS., 51–60, 2016. © 2014 Society of Plastics Engineers