Synthesis of Monodisperse Polymer Microspheres with Mercapto Groups and Their Application as a Stabilizer for Gold Metallic Colloid

Summary: Monodisperse polymer microspheres with functional mercapto groups on the surface were prepared from poly[(ethylene glycol dimethacrylate)‐co‐(2‐hydroxyethyl methacrylate)], poly(EGDMA‐co‐HEMA), microspheres successively through esterification of the active hydroxyl groups with acryloyl chloride to introduce carbon‐carbon double bonds and then the addition reaction of hydrogen sulfide to the double bond at pH 10–11. All of the polymer microspheres were characterized by scanning electron microscopy (SEM) and FT‐IR spectra. The mercapto‐functionalized polymer microspheres were utilized as a stabilizer for gold metallic colloids through coordination of the mercapto group on the polymer with gold metallic nanoparticles, which were prepared by the reduction of gold chloride trihydrate with sodium borohydride as the reductant. The size and morphology of the gold on the microspheres were determined to be of narrow dispersity (in the range 4–8 nm) by transmission electron microscopy (TEM).

Preparation of mercapto‐modified polymer microspheres and their application as a stabilizer for gold metallic colloids.     

Combining ATRP of Methacrylates and ROP of L,L‐Dilactide and ε‐Caprolactone

Coupling atom transfer radical polymerization (ATRP) and coordination‐insertion ring‐opening polymerization (ROP) provided a controlled two‐step access to polymethacrylate‐graft‐polyaliphatic ester graft copolymers. In the first step, copolymerization of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) was carried out at 80 °C at high MMA concentration by using ethyl 2‐bromoisobutyrate and [NiBr₂(PPh₃)₂] as initiator and catalyst, respectively. Kinetic and molar masses measurements, as well as ¹H NMR spectra analysis of the resulting poly(MMA‐co‐HEMA)s highlighted the controlled character of the radical copolymerization, while the determination of the reactivity ratios attested preferential incorporation of HEMA. The second step consisted of the ROP of ε‐caprolactone or L ,L ‐dilactide, in THF at 80 °C, promoted by tin octoate (Sn(Oct)₂) and coinitiated by poly(MMA‐co‐HEMA)s obtained in the first step. Once again, kinetic, molar mass, and ¹H NMR data demonstrated that the copolymerization was under control and started on the hydroxyl functions available on the poly(MMA‐co‐HEMA) multifunctional macroinitiator.

Comparison of the SEC traces for the poly(MMA‐co‐HEMA) macroinitiator P2 (line only), the polymethacrylate‐g‐PLA copolymer C2 (line marked by ○), and the polymethacrylate‐g‐PLA C3 (line marked by ?).     

Preparation and Characterization of Acetoacetoxyethyl Methacrylate‐Based Gels

Novel polymeric gels have been prepared by radical copolymerization of acetoacetoxyethyl methacrylate (AAEM) and hydroxyethyl methacrylate (HEMA) in water‐ethanol medium. The influence of the HEMA:AAEM ratio and crosslinker concentration on properties of gels was studied. Independently on gel composition the maximum swelling was detected in chloroform. It was found that PAAEM gels possess phase transition temperature or upper critical solution temperature (UCST) in alcohol‐water solutions. UCST decreases in linear order from 75 to 10 °C when HEMA content in gel structure increases. The minimal UCST of AAEM/HEMA gels in binary alcohol‐water mixtures is shifted toward lower temperatures and lower alcohol concentrations when the alkyl chain of alcohol increases.

AAEM/HEMA gels prepared at different BIS concentrations (1:1 mol‐%, 2:2.5 mol‐%, 3:5 mol‐%).     

Back‐Biting Termination in Methyl Methacrylate/tert‐Butyl Acrylate Anionic Block Copolymerization

The product of spontaneous termination formed after addition of one or two t‐BuA units onto living PMMA chains in the MMA/t‐BuA block copolymerization was isolated and characterized by SEC, UV, FT‐IR, Raman and NMR spectroscopy. It appears as a low‐molecular‐weight peak in SEC eluograms of the copolymers, absorbing at 260 nm; its retention time corresponds to that of the PMMA block. In its FT‐IR and Raman spectra, new bands appeared corresponding to the C?C and C?O vibrations of a conjugated and H‐bonded ester group of the enol form of the cyclic oxoester composed of MMA and t‐BuA units. Experimental support of a back‐biting reaction at the link between PMMA and Pt‐BuA blocks is presented.

     

Preparation of Fluorescent Carboxyl and Amino Functionalized Polystyrene Particles by Miniemulsion Polymerization as Markers for Cells

Summary: A series of fluorescent polystyrene latex particles with carboxyl and amino functionalities on their surface were synthesized by the miniemulsion technique. The fluorescent dye N‐(2,6‐diisopropylphenyl)perylene‐3,4‐dicarboximide (PMI) was incorporated into the copolymer nanoparticles formulated from styrene and acrylic acid or styrene and aminoethyl methacrylate hydrochloride. The resulting latexes were stable and showed a monodisperse size distribution. The particle size depended on the amount and nature of the functional comonomer and was in the range 100–175 nm. All latexes were characterized by transmission electron microscopy (TEM), dynamic light scattering, UV‐Vis spectroscopy and zeta potential measurements. The amount of surface functional groups was determined by electrolyte titration. Furthermore, the functionalized fluorescent particles were utilized as markers for HeLa cells and cell uptake was visualized using fluorescence microscopy. The correlation of the uptake of nanoparticles with the surface charge was determined by FACS measurements.

Confocal fluorescent microscopy of HeLa cells after the uptake of amino functionalized particles (green).     

Nanoscale Analysis of Polymer Interfaces by Energy‐Filtering Transmission Electron Microscopy

Summary: Energy‐filtering transmission electron microscopy (EFTEM) was employed for the analysis of polymer‐polymer interfaces. To attain imaging and spectral analyses with a spatial resolution of 10 nm, problems arising in the EFTEM analysis for polymer specimens were investigated. Interfaces in poly(methyl methacrylate)/polystyrene‐co‐polyacrylonitrile random copolymer (PMMA/SAN) bilayer films annealed at different temperatures were analyzed by means of elemental mapping and Image‐EELS on EFTEM and the effect of the annealing temperature on the interfacial structures was also investigated.

     

Combination of Mechanochemical Degradation of Polymers with Controlled Free‐Radical Polymerization

The result of ultrasound on polymer solutions is the breakage of macromolecular C C‐bonds due to cavitation. The fact that termination reactions of mechanoradicals as disproportionation and combination are suppressed in the presence of radical scavengers makes the following method possible. Thus the use of nitroxides acting as chain‐terminating agents allows the creation of macroinitiators which can be used in controlled free‐radical polymerization. In this work, we investigate the mechanochemical degradation of poly(methyl methacrylate) (PMMA) in the presence of OH‐TEMPO and the application of the irradiated polymers as macroinitiators in a controlled radical polymerization. The content of OH‐TEMPO terminated chains in the degraded product is determined by a computer‐aided procedure on the basis of molecular weight distributions.

Ultrasonic degradation of PMMA, decrease of molar mass (M _n), and polydispersity (Pd) as a function of irradiation time, power output = 200 W, ϑ = 45–50 °C.     

New Functionalized Anionic Initiators Prepared from Substituted 1,1‐Diphenylethylene Derivatives with Acetal‐Protected Monosaccharides and Their Application to Chain‐Multi‐Functionalized Polymers with Glucose and Galactose Molecules

Living anionic polymerizations of methyl methacrylate, tert‐butyl methacrylate, 2‐(perfluorobutyl)ethyl methacrylate, tert‐butyl acrylate, and ethylene oxide were carried out with functionalized initiators prepared from substituted 1,1‐diphenylethylene (DPE) derivatives with two and four acetal‐protected α‐D ‐glucofuranose and α‐D ‐galactopyranose residues and carbanionic species such as sec‐butyllithium (sec‐BuLi), cumylpotassium, lithium and potassium naphthalenides. In certain cases, either LiCl or diethylzinc was used as an additive to control the polymerization. Several new well‐defined chain‐end‐ and in‐chain‐functionalized polymers with two and four glucose and two galactose molecules were successfully synthesized by these living polymerizations followed by deprotection. We have proposed a promising iterative methodology based on a convergent approach, with which novel two dendritic substituted DPE derivatives with four and eight acetal‐protected D ‐glucofuranose residues can successively be synthesized. With use of the functionalized anionic initiators prepared from such dendritic DPE derivatives and sec‐BuLi in the polymerization of methyl methacrylate, well‐defined chain‐end‐functionalized poly(methyl methacrylate)s with four and eight glucose molecules were synthesized.

     

Pyrromethene 567 Dye as Visible Light Photoinitiator for Free Radical Polymerization

In the present work we report on the photochemistry and photopolymerization activity of a new bimolecular photoinitiator system, which exhibits maximum sensitivity at 518 nm, consists of a sensitizer dye, pyrromethene 567 (PM567), and a radical generating reagent 3,3′,4,4′‐tetra(tert‐butylperoxycarbonyl)benzophenone (BTTB). The photosensitization of BTTB through the excitation of PM567 induces high polymerization rates, while different experiences have revealed that PM567 or BTTB, separately, are unable of initiating the polymerization of 2‐hydroxyethyl methacrylate (HEMA) over extensive periods of time at 40 °C, either in the dark or under irradiation. The polymerization efficiency of this photoinitiator system, PM567/BTTB, was analyzed following the bulk polymerization kinetics of monomer HEMA by differential scanning photo‐calorimetry. Photopolymerization rates and quantum yields were observed under isothermal conditions (40 °C) for continuous illumination polymerizations (at 518 nm) at different incident light intensities and different BTTB concentrations.

Scheme of the photosensitization process of the bimolecular photoinitiator system of PM567/BTTB.     

MADIX Polymerization of Captodative Ethyl α‐Acetoxyacrylate with Acrylate Monomers

Summary: MADIX homopolymerization of a captodative monomer, ethyl‐α‐acetoxyacrylate (EAA) was investigated using AIBN as an initiator and O‐ethyl‐S‐(1‐methoxycarbonyl)ethyl dithiocarbonate as a transfer agent at 70 °C in a mixture of iPrOH and H₂O. The experimental results revealed that this transfer agent had no effect on the polymerization reaction when compared with a free radical polymerization. Copolymerization of ethyl‐α‐acetoxyacrylate, with different acrylic monomers, such as butyl acrylate (BuA), acrylic acid, N,N‐(dimethylamino)ethyl acrylate and N,N‐dimethyl acrylamide, was then studied by MADIX polymerization using the same transfer agent. All the prepared copolymers were characterized by ¹H NMR and size exclusion chromatography, and the obtained results were in accordance with theoretical predictions regarding molecular weight and copolymer composition. Futhermore, the living character of the polymerization has been checked by the chain extension of poly(EAA‐stat‐BuA) with vinyl acetate (Vac) which led to poly(EAA‐stat‐BuA)‐block‐poly(VAc).

     

Preparation of Polymeric Nanoparticles by Photo‐Crosslinking of an Acryloylated Polyaspartamide in w/o Microemulsion

Summary: Biodegradable polymeric nanoparticles have been prepared by UV irradiation of an acryloylated water soluble polymer by an inverse microemulsion. The starting polymer was a α,β‐poly(N‐2‐hydroxyethyl)‐D ,L ‐aspartamide (PHEA) partially functionalized with glycidyl methacrylate (GMA) in order to introduce reactive vinyl groups in the side chain. The PHEA‐GMA copolymer obtained (PHG) was crosslinked by UV irradiation of the inverse microemulsion prepared by mixing an aqueous solution of PHG with propylene carbonate (PC)/ethyl acetate (EtOAc) in the presence of sorbitan trioleate (SPAN 85) as surfactant. Nanoparticles obtained were characterized by FTIR spectrophotometry, transmission electron microscopy, size distribution analysis and zeta potential measurements. Nanoparticles investigated revealed spherical and homogeneous shading, the particle size having a mean diameter of 88 ± 13 nm (PDI = 0.21) and a negative surface charge in several aqueous media. Moreover, in vitro chemical and enzymatic hydrolysis studies evidenced the partial biodegradability of PHG nanoparticles, which is more evident after incubation with enzymes such as esterases. PHG nanoparticles were loaded during UV irradiation process with Cytarabine, chosen as a model drug, and Cyt‐loaded PHG nanoparticles were able to release it in a simulated physiological fluid (phosphate buffer at pH 7.4) and in blood plasma.

Transmission electron micrograph of photo‐crosslinked PHG.     

Swelling and Mechanical Properties of a Temperature‐Sensitive Dextran Hydrogel and its Bioseparation Applications

Summary: A series of temperature‐sensitive dextran hydrogels (poly(NIPA‐co‐GMA‐Dex)) were synthesized by the copolymerization of glycidyl methacrylate‐derivatized dextran (GMA‐Dex) and N‐isopropylacrylamide (NIPA) in aqueous solution. Their swelling and mechanical properties and bioseparation behaviors were studied. It is found that poly(NIPA‐co‐GMA‐Dex) hydrogels simultaneously exhibit much better swelling and mechanical properties. The interactions between poly(NIPA‐co‐GMA‐Dex) hydrogels and sodium dodecylsulfate (SDS), Rutin, and DL ‐α‐alanine were different because of their different hydrophobic nature, polarity, and molecular structure, and obviously depend on the temperature: the mechanism is discussed. In addition, using poly(NIPA‐co‐GMA‐Dex) hydrogels as the absorbents, gel‐extraction separation experiments of dextran and BSA solutions showed that the separation ability of poly(NIPA‐co‐GMA‐Dex) hydrogels obviously increased upon reaching the LCST.

Temperature dependence of the swelling ratio of the PNIPA (▪) and poly(NIPA‐co‐GMA‐Dex) hydrogels (r = 0.2(•), 0.4 (▴), 0.5 (▾), 0.6(♦), 0.8 (+)).     

Reactive Compatibilization of PA6/LDPE Blends with Glycidyl Methacrylate Functionalized Polyolefins

Summary: Blends of polyamide‐6 (PA6) and low density polyethylene (LDPE) were compatibilized by melt mixing with various polyolefins functionalized with glycidyl methacrylate (GMA), i.e., GMA grafted LDPE (LDPE‐g‐GMA), GMA grafted styrene‐ethylene/butylene‐styrene block copolymer (SEBS‐g‐GMA) and ethylene‐co‐glycidyl methacrylate copolymer (E‐GMA). Blends with PA6/LDPE composition ratios of 25/75 and 75/25 wt.‐%/wt.‐% were prepared in a Brabender internal mixer and their properties were evaluated by SEM, rheological measurements and DSC. Morphological investigation by SEM showed a neat improvement of phase dispersion and interfacial adhesion in all compatibilized blends when compared to PA6/LDPE binary blends. The variation of the dispersed phase size was analyzed as a function of blend composition, compatibilizer concentration and GMA content. The emulsification curves of compatibilized blends showed that the equilibrium size of dispersed particles at the saturation concentration of copolymer was lower when PA6 was the major component. The finest dispersion of the LDPE phase (<0.25 μm) was observed in the presence of SEBS‐g‐GMA copolymer. LDPE‐g‐GMA and E‐GMA displayed a similar compatibilizing efficiency. In all cases, the blends with a polyamide matrix presented a marked rise in torque and melt viscosity with increasing compatibilizer content. These effects were accounted for by a reaction between the epoxide groups of LDPE‐g‐GMA and the carboxyl/amine end‐groups of PA6, leading to the formation of an interchain graft copolymer. The phase transition processes of PA6 in the blends were influenced by the compatibilizer content and the interfacial interactions between the polymer components, suggesting a different role for the compatibilizer at the PA6/LDPE interface.

SEM micrograph of PA6/LDPE 25/75 blend compatibilized with 2.5 phr SEBS‐g‐GMA.     

Well‐Defined Miktocycle Eight‐Shaped Copolymers Composed of Polystyrene and Poly(ε‐caprolactone): Synthesis and Characterization

A series of well‐defined miktocycle number‐eight‐shaped copolymers composed of cyclic polystyrene (PS) and cyclic poly(ε‐caprolactone) (PCL) have been successfully synthesized by a combination of atom transfer radical polymerization (ATRP), ring‐opening polymerization (ROP), and “click” reaction. The synthesis involves three steps: 1) preparation of tetrafunctional initiator with two acetylene groups, one hydroxyl group and a bromo group; 2) preparation of two azide‐terminated block copolymers, N₃‐PCL‐(CH?C)₂‐PS‐N₃, with two acetylene groups anchored at the junction; and 3) intramolecular cyclization of the block copolymer through “click” reaction under high dilution. The ¹H NMR, FT‐IR, and gel permeation chromatography (GPC) techniques are applied to characterize the chemical structures of the resulting intermediates and the target polymers. Their thermal behavior is investigated by differential scanning calorimeter (DSC). The decrease in chain mobility of eight‐shaped copolymers restricts the crystallization of PCL.

     

Control of the radical polymerization by 2,2,15,15‐tetramethyl‐1‐aza‐4,7,10,13‐tetraoxacyclopentadecan‐1‐oxyl and its sodium salt

The control of the radical polymerization of styrene by 2,2,15,15‐tetramethyl‐1‐aza‐4,7,10,13‐tetraoxacyclopentadecan‐1‐oxyl is reported here in bulk at 90 °C, 120 °C and in miniemulsion. Similarly, the control by its sodium complex is reported in bulk at 90 °C.

M _n vs. conversion for 3 , 3Na , and TEMPO.     

Preparation of Carboxyl‐Functionalized Polystyrene/Silica Composite Nanoparticles

Summary: This paper describes the synthesis of carboxyl‐functionalized polystyrene/silica (PS/SiO₂) composite nanoparticles with various contents of poly(methacrylic acid) (PMAA) on the surface by post‐addition of methacrylic acid (MAA) via emulsion polymerization. High yields and binding efficiencies (around 90%) are achieved by an optimal procedure mainly involving the appropriate addition of MAA and amounts of surfactant and silica. The kinetics investigated indicates that the polymerization follows a mechanism different than that found in some earlier studies. The amount of grafted PMAA was determined by titration and FT‐IR, and altered in a wide range (1–40 wt.‐% to PS). Transmission electron microscopy (TEM) photographs show that the composite nanoparticles are about 60 nm in spherical shape and have a multi‐layered core‐shell structure with a cluster of primary silica beads as the core and PMAA as the outmost shell. There are approximately 4 to 21 primary silica beads in one composite nanoparticle, depending on the amount of silica added.

Preparation of carboxyl‐functionalized polystyrene(PS)/silica composite nanoparticles.     

Hyperbranced Polymers by Photoinduced Self‐Condensing Vinyl Polymerization Using Bisbenzodioxinone

Branched polymers with different branching densities and their cross‐linked analogues are synthesized by photoinduced self‐condensing vinyl polymerization via benzodioxinone photochemistry. Thus, methyl methacrylate is copolymerized with two different comonomers, namely, 2‐hydroxyethyl methacrylate (HEMA) and 2‐(dimethylamino)ethyl methacrylate in the presence of bisbenzodioxinone (BBNZ) under UV light. Upon irradiation, BBNZ undergoes irreversible decomposition leading to the formation of benzophenone photosensitizer and bisketene. The released benzophenone is further photoexcited at the same wavelength to give the initiating radicals through hydrogen abstraction from the inimer. In the case of HEMA, additional branching sites are formed by the reaction of bisketene with the hydroxyl functionalities of HEMA.

     

Synthesis of Amine and Epoxide Telechelic Siloxanes

A synthetic route was developed to prepare thermosetting methyl, cyclopentyl, and cyclohexyl substituted polysiloxanes with epoxide or amino end groups. Cycloalkene (cyclopentene or cyclohexene) and dichlorosilane gas were reacted at 180 °C, and at high pressure (2 MPa) to produce dicycloaliphatic dichlorosilane. Hydrolytic condensations of the dichlorosilanes were performed affording low molecular weight cyclic siloxane oligomers. Base catalyzed ring opening polymerization of the cyclic oligomers afforded the hydride‐terminated polysiloxanes. The hydride‐terminated polysiloxanes were then functionalized with glycidyl epoxide or aliphatic amine groups via hydrosilation reactions. The oligomers and polymers were characterized by ¹H NMR, ¹³C NMR, ²⁹Si NMR, FTIR, and GPC. The molecular weight of polydimethylsiloxane, polydicyclopentylsiloxane, and polydicyclohexylsiloxane oligomers were = 1 000, 1 200, and 1 500, respectively. The polydispersity index of all the cyclic oligomers was ≈1.15. Differential scanning calorimetry (DSC) was used to evaluate the crosslinking reaction and the glass transition temperature of the thermally cured systems. Crosslinking occurred at 120 °C and the T_g of the methyl, cyclopentyl, and cyclohexyl functionalized siloxanes were found to be at ?104, ?93, and ?82 °C, respectively.

     

Dielectric Study of the Effect of a Sol‐Gel Inorganic Network on Polymeric Relaxation Dynamics in Acrylic/Titania Hybrids

Summary: In this research, poly[(methyl methacrylate)‐co‐(butyl methacrylate)‐co‐(methacrylic acid)]/TiO₂ hybrids were prepared by the sol‐gel process. The copolymer composition was 16 mol‐% methyl methacrylate (MMA), 80 mol‐% butyl methacrylate (BMA) and 4 mol‐% methacrylic acid (MA). The dielectric properties of the hybrids with varying titania content were measured over the frequency range 0.1 Hz to 100 kHz and between 25 and 160 °C. In addition, the hybrids were investigated using differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). In the given frequency range, a single relaxation peak was observed both by dielectric relaxation spectroscopy (DRS) and DMTA. The single relaxation observed by DRS behaves in the manner of an α‐relaxation, with the frequency–temperature locus showing non‐Arrhenius behavior (curved downwards like a VTF law). The change in the DRS and DMTA characteristics in hybrids compared to the pure polymer reflect the presence of antagonistic mechanisms controlling the dynamics of the polymer chains: nanodomains with enhanced and restricted mobilities are suggested to be responsible for the broadening of the isochronal dielectric loss curve toward, respectively, the low and the high temperature sides. Combining the DSC and DRS results, it can be inferred that the domains with enhanced mobility result from internal and external plasticization effects that reduce the intermolecular hydrogen bonds between the polymer chains. Besides, the motion of polymer chains is found to be significantly hindered by the titania network, due to the presence of iono‐covalent bonds between the polymer and titania and geometrical restrictions in high junction‐point density and titania‐rich microphases. From the Arrhenius plot, it is also shown that the addition of sol‐gel titania more severely hinders the segmental motion of the macromolecular chains than the local motion of the lateral groups (β relaxation).

Simplified schematic morphology for the poly(MMA‐co‐BMA‐co‐MA)/TiO₂ hybrids.     

Organic‐Inorganic Hybrid Membranes for Removal of Benzene from an Aqueous Solution by Pervaporation

Summary: Preparation of organic‐inorganic hybrid membranes and their pervaporation permeation and separation characteristics for an aqueous solution of 0.05 wt.‐% benzene are described. In this study, we prepared organic‐inorganic hybrid membranes by the sol‐gel reaction of tetraethoxysilane (TEOS) as an inorganic component with poly(methyl methacrylate‐co‐vinyltriethoxysilane) (P(MMA‐co‐VTES)) and poly(butyl methacrylate‐co‐vinyltriethoxysilane) (P(BMA‐co‐VTES)) as organic components. When an aqueous solution of dilute benzene (0.05 wt.‐%) was permeated through the P(MMA‐co‐VTES)/TEOS and P(BMA‐co‐VTES)/TEOS hybrid membranes, the benzene concentration in the permeate through all hybrid membranes was higher than that in the feed solution. This result demonstrates that these hybrid membranes are benzene selective for an aqueous solution containing dilute benzene. The benzene/water selectivity of the P(BMA‐co‐VTES)/TEOS hybrid membrane was about 20 times higher than that of the P(MMA‐co‐VTES)/TEOS hybrid membrane. Specifically, the P(BMA‐co‐VTES)/TEOS hybrid membrane with a TEOS content of 75 mol‐% showed the highest benzene/water selectivity. The benzene/water selectivity of the hybrid membranes depended significantly on the cross‐linked structures formed by the sol‐gel reaction of VTES and TEOS.

Effects of the TEOS content on the sorption selectivity (○) and the diffusion selectivity (?) for an aqueous solution of 0.05 wt.‐% benzene through P(MMA‐co‐VTES)/TEOS and P(BMA‐co‐VTES)/TEOS hybrid membranes at 40 °C.