Graft copolymers via combination of cationic polymerization and atom transfer radical polymerization and their phase separation into spherical/worm-like nanostructures

Poly(p-chloromethyl styrene)-graft-poly(methyl methacrylate) (PCMS-g-PMMA) and poly(p-chloromethyl styrene)-graft-poly(benzyl methacrylate) (PCMS-g-PBzMA) graft copolymers with asymmetric branches are synthesized via the combination of cationic polymerization and atom transfer radical polymerization (ATRP). The process involves first, the preparation of poly(p-chloromethyl styrene) (PCMS-CH₂Cl) macroinitiator without any cross-linking or side reactions through pendant benzyl chloride (?CH₂Cl) functionality by cationic polymerization using a simple FeCl₃-based initiating system at 25 °C. The as-synthesized PCMS-CH₂Cl, without any transformation, is then used as the macroinitiator to graft PMMA and PBzMA branches by ATRP to produce PCMS-g-PMMA and PCMS-g-PBzMA graft copolymers of varying compositions with controlled molecular weight and moderately narrow polydispersities (M _w/M _n?≤?1.32). The resulting PCMS₂₁ -g-PMMA₂₃₂ graft copolymer in thin film form phase separates into spherical morphology with an average diameter of 170?±?72 nm. Whereas the PCMS₂₁ -g-PBzMA₁₅₆ graft copolymer gives worm-like nanostructures with an average length of 94 nm and width of 31 nm due to phase separation as visualized through atomic force microscopy. On the other hand, the phase-separated morphology is not very well-defined for other graft copolymers (PCMS₁₁₃ -g-PMMA₂₂₇ and PCMS₁₁₃ -g-PBzMA₁₅₄) thin films containing longer PCMS chains. This approach represents a rapid and convenient route to prepare unique spherical/worm-like polymer nanostructures. Figure

Well-defined poly(p-chloromethyl styrene)-graft-poly(methyl methacrylate) (PCMS-g-PMMA) and poly(p-chloromethyl styrene)-graft-poly(benzyl methacrylate) (PCMS-g-PBzMA) graft copolymers with asymmetric branches are synthesized by the combination of living cationic polymerization and atom transfer radical polymerization (ATRP). The resulting PCMS₂₁ -g-PMMA₂₃₂ and PCMS₂₁ -g-PBzMA₁₅₆ graft copolymers phase separate into nanostructured spherical and worm-like morphologies, respectively, in thin film form. The phase-separated morphology is not very well-defined for graft copolymers (PCMS₁₁₃ -g-PMMA₂₂₇ and PCMS₁₁₃ -g-PBzMA₁₅₄) thin films containing longer PCMS chains.     

A sensor based on incorporating Ni2+ into ZnO nanoparticles-multi wall carbon nanotubes-poly methyl metacrylat nanocomposite film modified carbon paste electrode for determination of carbohydrates

The ZnO nanoparticles (ZnONPs) were synthesized with gelatin as stabilizer via the sol-gel method and were characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). An electrochemical sensor based on ZnO nanoparticles-multi wall carbon nanotubes-poly methyl metacrylat (ZnONPs-MWCNT-PMMA) composite film was developed by incorporating Ni²⁺ into the ZnONPs-MWCNT-PMMA film modified carbon paste electrode (Ni²⁺/ZnONPs-MWCNT-PMMA/CPE). The electrochemical activity of Ni²⁺/ZnONPs-MWCNT-PMMA/CPE was illustrated in 0.10 M NaOH using cyclic voltammetry. The Ni²⁺/ZnONPs-MWCNT-PMMA/CPE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple. Ni²⁺/ZnONPs-MWCNT-PMMA/CPE also show good electrocatalytic activity toward the oxidation of carbohydrates (glucose, fructose and sorbitol). The Ni²⁺/ZnONPs-MWCNT-PMMA/CPE gives a good linear range with a detection limit of 8, 6, and 9 μM towards the determination of glucose, fructose and sorbitol, respectively by amperometry. Furthermore, the modified sensor was successfully applied to the sensitive determination of carbohydrates in real samples.     

Miscibility and crystallization behaviors of stereocomplex-type poly(l- and d-lactide)/poly(methyl methacrylate) blends

Stereocomplex-poly(l- and d-lactide) (sc-PLA) and poly(methyl methacrylate) (PMMA) blends were prepared by solution blending at PMMA loadings from 20 to 80 mass%. The miscibility and crystallization behaviors of the blends have been studied in detail by differential scanning calorimeter. The single-glass transition temperatures (T _g) of the blends demonstrated that the obtained system was miscible in the amorphous state. It was observed that the crystallization peak temperature of sc-PLA/PMMA blends was marginally lower than that of neat sc-PLA at various cooling rates, indicating the dilution effect of PMMA on the sc-PLA component to restrain the overall crystallization process. In the study of isothermal crystallization kinetics, the reciprocal value of crystallization peak time ( \( t_{\text{p}}^{ - 1} \) ) decreased with increasing PMMA content, indicating that the addition of non-crystalline PMMA inhibited the isothermal crystallization of sc-PLA at an identical crystallization temperature (T _c). Moreover, the negative value of Flory–Huggins interaction parameter (χ ₁₂ = ?0.16) of the blend further indicated that sc-PLA and PMMA formed miscible blends.     

Characterization of poly(2-vinylpyridine)-block-poly(methyl methacrylate) copolymers and blends of their homopolymers by liquid chromatography at critical conditions

Poly(2-vinylpyridine)s (P2VPs) are important polymers with extensive applications in modern day material science. P2VP is an exceptional case for liquid chromatography because of certain polar interactions with most of the stationary phases. In the present study, we established the critical adsorption point (CAP) of P2VP for the first time. The effectiveness of the method is demonstrated by analyses of blends and block copolymers of P2VP and PMMA. The CAP of PMMA is established for determination of molar mass of P2VP component of above mentioned blends and block copolymers. The methods successfully demonstrate the separation of both types of homopolymers from the rest of the samples in conjunction with the determination of molar mass distribution of noncritical block or component. Graphical Abstract

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Preparation of stable gold nanoparticles by using diblock copolymer mixture as encapsulating agent

Gold nanoparticles by using the mixture of polystyrene-block-poly(2-vinyl pyridine)/poly(2-vinyl pyridine)-block-poly(ethylene oxide) (PS-b-P2VP/P2VP-b-PEO) block copolymers as encapsulating agent was prepared. The prepared nanoparticles were characterized by transmission electron microscopy, UV-Vis spectroscopy and contact angle. It is demonstrated that the obtained gold nanoparticles are covered with mixed block copolymer shells. The hydrophilic property of the nanoparticles can be varied by the change of the dispersion medium. The obtained gold nanoparticles with mixed block copolymer shells are stable in organic solvents (such as tetrahydrofuran and toluene) and water.     

Thermal decomposition of polymethylmethacrylate synthesized with anionic catalysts

TG and DTA data are used to show that the thermal decomposition of polymethylmethacrylate (PMMA) synthesized with anionic catalysts depends on the nature of the catalyst. It is found that the thermal stability of PMMA obtained by using anionic amide catalysts is higher than that of radical PMMA and of PMMA obtained with other anionic catalysts, and depends on the temperature of polymerization and on the molecular weight of the polymer.     

Poly(N-isopropylacrylamide)-block-poly(acrylic acid) hydrogels: synthesis and rapid thermoresponsive properties

In this contribution, we reported the synthesis of poly(N-isopropylacrylamide)-block-poly(acrylic acid) (PNIPAAm-b-PAA) copolymer networks via sequential reversible addition-fragmentation chain transfer (RAFT) polymerization. The PNIPAAm-b-PAA block copolymer networks were characterized by means of Fourier transform infrared spectroscopy (FTIR) and small angle X-ray scattering (SAXS). The volume phase transition (VPT) temperatures of the PNIPAAm-b-PAA hydrogels were measured by means of micro-differential scanning calorimetry (micro-DSC). It was found that the block copolymer hydrogels displayed the VPT temperatures lower than the control PNIPAAm hydrogel. Compared to the control PNIPAAm hydrogel, the deswelling and reswelling properties of the block copolymer hydrogels were significantly improved. The improved thermoresponsive properties of the PNIPAAm-b-PAA hydrogels have been interpreted on the basis of the formation of the architecture of the block copolymer networks.     

Evaluation of flame retardancy and shear resistivity characteristics of organoclay within acrylate polymer

The present work focuses on the effect of organically modified nanoclays on the fire resistance and processability characteristics of poly(methyl methacrylate) (PMMA). PMMA nanocomposite of cloisite 30B (methyl tallow bis-2 hydroxyethyl quarternary ammonium salt modifier) (C30B) was prepared by melt blending technique. A comparative study of flame retardant characteristics of virgin and filled matrix was carried out using cone calorimeter at a heat flux of 50 kW m^?2, and the service temperature range was analyzed from thermogravimetric analysis. Parallel plate rheometry revealed the variation in processability as a function of C30B reinforcement and corresponding melt strength of the samples was evaluated through complex viscosity, storage, and loss modulus. Similarly, application-level modulus values were evaluated through viscoelastic properties by dynamic mechanical analysis. Supportive information for the observations from the above characterization was conducted using morphological studies by X-ray diffraction and transmission electron microscopy.     

Incorporation of Dyes into Polystyrene-block-poly(4-vinylpyridine) Nanotemplates

Summary: The present study provides some basic concepts of functionalization of diblock copolymer (BC) nanotemplates for optical applications. It is focused on the polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) building medium which is suitable for hydrogen bonding, undergoes phase segregation, and is well-accessible. Two techniques are described and demonstrated on several dye complexes with PS-b-P4VP. Relation between optical properties and thin film structure is tentatively studied in dependence on solvent effects in thin films.     

Formation of gold nanoparticles in diblock copolymer micelles with various reducing agents

Gold nanoparticles (Au NPs) were prepared by the reduction of HAuCl₄ acid incorporated into the polar core of poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer micelles dissolved in toluene. The formation of Au NPs was controlled using three reducing agents with different strengths: hydrazine (HA), triethylsilane (TES), and potassium triethylborohydride (PTB). The formation of Au NPs was followed by transmission electron microscopy, UV–Vis spectroscopy, isothermal titration calorimetry (ITC), and dynamic light scattering (DLS). It was found that the strength of the reducing agent determined both the size and the rate of formation of the Au NPs. The average diameters of the Au NPs prepared by reduction with HA, TES, and PTB were 1.7, 2.6, and 8 nm, respectively. The reduction of Au(III) was rapid with HA and PTB. TES proved to be a mild reducing agent for the synthesis of Au NPs. DLS measurements demonstrated swelling of the PS-b-P2VP micelles due to the incorporation of HAuCl₄ and the reducing agents. The original micellar structure rearranged during the reduction with PTB. ITC measurements revealed that some chemical reactions besides Au NPs formation also occurred in the course of the reduction process. The enthalpy of formation of Au NPs in PS-b-P2VP micelles reduced by HA was determined.     

A colorimetric assay for d-Penicillamine in urine and plasma samples based on the aggregation of gold nanoparticles

We report herein the development of a highly sensitive colorimetric method for detection of d-Penicillamine using citrate-capped gold nanoparticles (AuNPs). This assay relies upon the distance-dependent of gold nanoparticles surface plasmon resonance band of gold nanoparticles. By replacing the thiol-containing chelator drug, d-Penicillamine, with citrate on the gold nanoparticles surface, a new peak appearing at a longer wavelength intensifies and shifts further to the red from the original peak position due to aggregation of gold nanoparticles which depends on ionic strength, gold nanoparticles and d-Penicillamine concentration. During this process, the plasmon band at 521 nm decreases gradually along with the formation of a new red-shifted band at 630 nm. The calibration curve which is derived from the ratio intensities of absorbance at longer wavelength (630 nm) to original wavelength (521 nm) displays a linear relation in the range of 5.0 × 10^?6–3.0 × 10^?4 M d-Penicillamine. Lower limit of detection for d-Penicillamine, at the signal-to-noise ratio of 3 (3σ), was 3.8 × 10^?6 M. The developed methodology was successfully applied for the determination of d-Penicillamine in human urine and plasma.     

A simple method to prepare highly ordered PS-b-P4VP block copolymer template

A control strategy for tuning the film morphology of asymmetric polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers (BCPs) is reported. After preparation of the film by spin-coating method, the as-cast films were annealed in different solvent vapor. It is found that chloroform is a wonderful solvent for forming PS-b-P4VP regular pattern. Otherwise, with changing the concentration of PS-b-P4VP, cylindrical or parallel nanostructures could be attained. The PS-b-P4VP films with cylindrical structure are used as template to deposit FePt nanoparticles into the pores. Nanoparticles reaching the bottom of the holes form a disordered magnetic array.     

Reverse atom transfer radical polymerization of methyl methacrylate in the presence of Azo-functionalized carbon nanotubes: a grafting from approach

After oxidation of carbon nanotubes (CNT), its carboxyl groups were subsequently converted to acyl chloride and hydroxyl functionalities. Subsequently, 4,4′-azobis (4-cyanopentanoic acid) (ACPA) was attached to the hydroxyl groups of nanotubes by an esterification reaction to yield azo initiator-anchored nanotubes (CNTAzo). Then, grafting from reverse atom transfer radical polymerization of methyl methacrylate in the presence of CNTAzo in different weight percents was carried out. Appearance of N_1s band in the spectrum of CNTAzo originates from the covalent attachment of ACPA on CNT. Successful functionalization of CNT with EG, ACPA, and PMMA was also proved by FTIR. SEC results show that molecular weight and PDI values of the attached chains are higher. XRD and Raman spectroscopy were used to study the structural characteristics of the CNTs. Graft density of modifier and PMMA in various CNTs was evaluated by TGA. Finally, morphology of the CNTs was studied by scanning and transmission electron microscopies.     

Dehydrogenation of 4-aryl(hetaryl) spinacine derivatives with dimethyl sulfoxide

Aromatization of 4-aryl(hetaryl)tetrahydroimidazo[4,5-c]pyridine-6-carboxylic acids and their lithium salts by the action of dimethyl sulfoxide has been revealed for the first time. Heating of these compounds in DMSO for 5–7 h at 90–95°C leads to the formation of 4-aryl(hetaryl)imidazo[4,5-c]pyridine derivatives as a result of dehydrogenation and decarboxylation. Heating of the corresponding lithium salts generated in situ (DMSO, 90–95°C, 3–5 h) affords difficultly accessible 4-aryl(hetaryl)imidazo[4,5-c]pyridine-6-carboxylic acids.     

pH-responsive star-shaped functionalized poly(ethylene glycol)-b-poly(ε-caprolactone) with amino groups

Functional star-shaped 4-arm poly(ethylene glycol)-b-poly[(ε-caprolactone-co-γ-amino-ε-caprolactone)] (4-arm PEG-b-P(CL-co-ACL) was synthesized through ring-opening polymerization. The structure of the copolymer was confirmed by ¹H NMR, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). To further understand the copolymers, the difference of the conversion rate between ε-caprolactone (CL) and γ-(carbamic acid benzyl ester)-ε-caprolactone (CABCL) and the detailed deprotection condition were studied. The thermal property of the copolymer was analyzed by WAXR and differential scanning calorimetry (DSC), which demonstrated that the thermal property could be well adjusted. The pH-responsive behavior of the copolymers was studied in detail by dynamic light scattering (DLS), pH titration, and pyrene fluorescence methods, which indicated that it could form micelles and exhibit pH responsibility. Moreover, the copolymer was nontoxic and had good biocompatibility according to the results by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay.     

Spin-trapped Radicals: Determination by LC-TSP-MS and LC-ESI-MS

The 4-POBN[α-(4-pyridyl-l-oxide)-N-tert-butyl-nitrone] radical adducts of ethyl and pentyl radicals were determined by a combination of high performance liquid chromatography (HPLC) combined with electron paramagnetic resonance (EPR) with HPLC-electrospray (ESI)-mass spectrometry and HPLC-thermospray (TSP)-MS. The identifIcation of the peak corresponding to the spin-trapped radical was done by performing HPLC-EPR under the same chromatographic conditions as the HPLC-MS. The radical adducts could be determined by both techniques, even though for ESI only 12 μL/min of the total 1 mL/min HPLC flow rate could be directed into the ion source.     

A strategy to stabilize the confined chiral TPPS J-aggregate by ionic block copolymer

Poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP), with a poly-cation building block, forms electrostatic complexes with the J-type chiral pre-aggregates of 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrin (TPPS) in the water inner-phase of the TX-100 reverse microemulsion at pH 1.0 using l-tryptophan as the chiral source. The complexation with PEG₄₅-b-P4VP₆ prevents these chiral pre-aggregates from contacting with each other during the percolation of the droplets, so as to stabilize the circular dichroism intensity and the size of the complexes. After breaking the microemulsion, the PEG₄₅-b-P4VP₆/TPPS aggregates are also prevented from further clustering at optimized ratio of [polymer]/[TPPS], so these complex aggregates disperses in acetone with spherical morphology and well maintain their size and chiral signal for further storing. This method can be considered as one of extracting the confined chiral aggregates as an isolated form apart from the reverse microemulsion.     

The Prognostic Value of Histidine-Rich Glycoprotein RNA in Breast Tissue Using Unmodified Gold Nanoparticles Assay

The aim of is this study is to explore the role of tissue histidine-rich glycoprotein (HRG) RNA as a promising clinically useful biomarker for breast cancer patients prognosis using nanogold assay. Expression of the HRG RNA was assessed by gold nanoparticles and conventional RT-PCR after purification by magnetic nanoparticles in breast tissue samples. The study included 120 patients, 60 of which were histologically proven breast carcinoma cases, 30 had benign breast lesions and 30 were healthy individuals who had undergone reductive plastic surgery. ER, PR and HER2 status were also investigated. The prognostic significance of tissue HRG RNA expression in breast cancer was explored. The magnetic nanoparticles coated with specific thiol modified oligonucleotide probe were used successfully in purification of HRG RNA from breast tissue total RNAs with satisfactory yield. The developed HRG AuNPs assay had a sensitivity and a specificity of 90 %, and a detection limit of 1.5 nmol/l. The concordance rate between the HRG AuNPs assay with RT-PCR after RNA purification using magnetic nanoparticles was 93.3 %. The median follow-up period was 60 months. Among traditional prognostic biomarkers, HRG was a significant independent prognostic marker in relapse-free survival (RFS). HRG RNA is an independent prognostic marker for breast cancer and can be detected using gold NPs assay, which is rapid, sensitive, specific, inexpensive to extend the value for breast cancer prognosis.     

Debundling of multiwalled carbon nanotubes in N,N-dimethylacetamide by polymers

Structure and properties of the dispersions of multiwalled carbon nanotubes (MWCNTs) in N,N-dimethylacetamide (DMAc) with different dispersing polymers: polyvinylpyrrolidone (PVP), poly(ethyleneoxide), triblock copolymers poly(ethyleneoxide)-b-poly(propyleneoxide)-b-poly(ethyleneoxide) (Pluronic F127 and Pluronic F108), ethylenediamine tetrakis(ethoxylate-b-propoxylate) tetrol, and ethylenediamine tetrakis(propoxylate-b-ethoxylate) tetrol (Tetronic) of different molecular weights were studied. All studied polymers were shown to be able to disperse MWCNT in DMAc, and MWCNT dispersions appear free of aggregates by visual inspection even after 3 months of keeping at room temperature. Dispersions were characterized by UV–VIS absorption spectroscopy and dynamic light scattering measurements. PVP was found to be the best dispersing polymer for MWCNT in DMAc. It was shown that the yield of the dispersed MWCNT and the average particle size of the MWCNT in DMAc depend on the chemical nature, molecular weight of the dispersing polymer, and solvent quality. The difference in dispersive capacity of the studied polymers is attributed to different dispersion mechanisms for PVP (“polymer wrapping” model) and for other studied dispersing polymers (“loose adsorption” model), which have different efficiencies in DMAc. It was revealed that an increase of dispersing polymer (PVP) concentration at the range of 4.7–37.6 g l^?1 results in an average particle size enlargement and MWCNT final concentration reduction.