Preparation of microspheres with silicone oil cores and poly(N‐isopropylacrylamide) shells by physical coating

Surfactant‐free thermoresponsive microspheres with a silicone oil cores surrounded by poly(N‐isopropylacrylamide) shells have been successfully prepared by physical coating method for the first time. The influences of reaction temperature, N‐isopropylacrylamide (NIPAM) dosage, and stirring rate on the formation, morphology, particle size, and monodispersity of microspheres were experimentally studied. In the preparation of microspheres, when reaction temperature was above the lower critical solution temperature of poly(N‐isopropylacrylamide), products had higher yield of particles and narrower size distribution. With increasing NIPAM dosage, the particle diameter became larger and the shell layer thickened and the monodispersity became better. With increasing stirring rate, the particle diameter and the monodispersity decreased obviously. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5571–5576, 2006     

Swelling behavior of semi‐interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(acrylamide‐co‐sodium methacrylate)

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and poly(acrylamide‐co‐sodium methacrylate) poly(AAm‐co‐SMA) were prepared by the semi IPN method. These IPN hydrogels were prepared by polymerizing aqueous solution of acrylamide and sodium methacrylate, using ammonium persulphate/N,N,N¹,N¹‐tetramethylethylenediamine (APS/TMEDA) initiating system and N,N¹‐methylene‐bisacrylamide (MBA) as a crosslinker in the presence of a host polymer, poly(vinyl alcohol). The influence of reaction conditions, such as the concentration of PVA, sodium methacrylate, crosslinker, initiator, and reaction temperature, on the swelling behavior of these IPNs was investigated in detail. The results showed that the IPN hydrogels exhibited different swelling behavior as the reaction conditions varied. To verify the structural difference in the IPN hydrogels, scanning electron microscopy (SEM) was used to identify the morphological changes in the IPN as the concentration of crosslinker varied. In addition to MBA, two other crosslinkers were also employed in the preparation of IPNs to illustrate the difference in their swelling phenomena. The swelling kinetics, equilibrium water content, and water transport mechanism of all the IPN hydrogels were investigated. IPN hydrogels being ionic in nature, the swelling behavior was significantly affected by environmental conditions, such as temperature, ionic strength, and pH of the swelling medium. Further, their swelling behavior was also examined in different physiological bio‐fluids. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 302–314, 2005     

Dispersion of non-covalently functionalized single-walled carbon nanotubes with high aspect ratios using poly(2-dimethylaminoethyl methacrylate-co-styrene)

Single-walled carbon nanotubes (SWCNTs) with high aspect ratios were well dispersed in organic solvents to form stable suspensions using poly(2-dimethylaminoethyl methacrylate-co-styrene) (poly(DMAEMA-co-St)). The polymeric dispersant poly(DMAEMA-co-St) was synthesized in various compositions by atom transfer radical polymerization. The structures and the compositions of the poly(DMAEMA-co-St) were confirmed by ¹H NMR spectroscopy. The stability and dispersion of the functionalized SWCNTs with high aspect ratios in suspension were observed by dispersion stability analysis, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. The existence of unbundled SWCNTs was confirmed by Raman and ultraviolet/visible/near-infrared spectroscopy. Finally, SWCNT transparent conductive films with high transmittances and low sheet resistances were prepared on a poly(ethylene terephthalate) substrate using a spin-coating method.     

Monitoring of swelling of interpenetrating polymer network of polyethylene/poly(styrene-co-butylmethacrylate) (PE/P(S-co-BMA)) in toluene and cyclohexane using fluorescence spectroscopy

A real-time monitoring of excimer emission fluorescence probe di(1-pyrenemethyl)ether (DiPyM) was used for study swelling interpenetrating polymer network (IPN) consisting of polyethylene/poly(styrene-co-butylmethacrylate) (PE/P(S-co-BMA)) and containing different network density. DiPyM was introduced into IPN during polymerisation or was penetrated into blocks from toluene solution. The effect of solvent quality for swelling of IPN and density of IPN network was also studied. From steady-state measurements of monomer and excimer emission ratio (I_e/I_m), no difference was found between rate of swelling IPN with 0.5, 1 and 3 mol% of cross-linker. The rate of IPN swelling seems to be rather high. Some differences was found at real-time monitoring of excimer emission (λ_em=495 nm) of DiPyM measured during desorption of DiPyM from swelled IPN blocks. At higher content of cross-linker, a slower rate of DiPyM desorption from IPN matrix was observed.     

Synthesis of vinylferrocene and the ligand-exchange reaction between its copolymer and carbon nanotubes

To improve the dispersibility of carbon nanotubes (CNTs), poly(vinylferrocene-co-styrene) (poly (Vf-co-St)), was grafted onto the surface of CNTs by a ligand-exchange reaction. Poly(Vf-co-St) was obtained by a radical copolymerization reaction using styrene and vinylferrocene as the monomers. The vinylferrocene was synthesized from ferrocene via a Friedel-Crafts acylation. The molecular weight, molecular weight distribution, and amount of Vf in the poly(Vf-co-St) were 1.32 × 10⁴, 1.69 and 17.6% respectively. The degree of grafting of the copolymer onto the CNTs surface was calculated from thermogravimetric analysis and varied from 27.1% to 79.7%. The addition of the poly(Vf-co-St) greatly promoted the dispersibility of the modified CNTs in anhydrous alcohol. The electrical conductivity of composites prepared from the polymer-grafted CNTs and copolymer (acrylonitrile, 1,3-butadiene and styrene, ABS) strongly depended on the degree of grafting. These results show that the amount of polymer grafted onto the surface of CNTs can be controlled and that the electrical properties of composites prepared with these grafted polymers can be tuned.     

Dual thermo-responsive and ion-recognizable monodisperse microspheres

A novel type of dual stimuli-responsive microspheres that simultaneously exhibit ion-recognition property based on the supramolecular host-guest complexation of crown ether receptors (benzo-18-crown-6-acrylamide) (BCAm) with specific ions and thermo-sensitivity based on the phase transition of poly(N-isopropylacrylamide) (PNIPAM) is fabricated in this study. The prepared poly(N-isopropylacrylamide-co-benzo-18-crown-6-acrylamide) (P(NIPAM-co-BCAm)) microspheres are characterized by FT-IR spectroscopy, UV-vis absorption spectroscopy, scanning electron microscopy (SEM), and dynamic light scattering (DLS). SEM images and DLS data show that the synthesized microspheres exhibit nearly perfect spherical shape and high monodispersity. Moreover, according to the DLS results, P(NIPAM-co-BCAm) microspheres exhibit satisfactory thermo-responsive behavior and ion-recognition property. In K⁺ solutions, due to the formation of crown ether/K⁺ complexes, the LCST of P(NIPAM-co-BCAm) microspheres shifts to a higher temperature and the colloidal stability is increased. The P(NIPAM-co-BCAm) microspheres undergo a volume change from shrunken state to swollen network isothermally at a certain temperature by the addition of metal ions. Due to dual thermo-responsive and ion-recognition behaviors, this kind of microspheres would serve as promising candidates for sensors, controlled drug delivery systems and possibly new biomaterials.     

互穿网络敏感型聚氨酯水凝胶的合成与研究

以异佛尔酮二异氰酸酯（IPDI）、聚氧化丙烯二醇（PPG-220）、二羟甲基丙酸（DMPA）、蓖麻油（C0）等为主要原料,合成交联型水性聚氨酯乳液,在此乳液中加入丙烯酰胺、引发剂（KPS）,交联剂（BMA）进行自由基聚合,制备具有IPN结构的聚氨酯-聚丙烯酰胺（PU—PAAm）水凝胶。研究了（PU—PAAm）水凝胶溶胀率（SR）受pH值、温度（T）、交联剂用量等因素的影响。     

Morphology of the transparent IPN‐like system PE: (BMA‐co‐S)

In the study of interpenetrating polymer networks (IPN)‐like systems consisting of polyethylene (PE) and butyl methacrylate (BMA)–styrene (S) copolymer PE/(BMA‐co‐S), the effect of the crosslinker on the morphology of IPN by using electron microscopy and atomic force microscopy (AFM) was investigated. The IPN‐like system PE/(BMA‐co‐S) represents a two‐phase system with finely dispersed domains of crosslinked PE matrix. The interphase between dispersed domains and PE matrix is inhomogeneous and is considered the most interpenetrated part of this IPN‐like system. The size of the domains decreases with the content of crosslinker used. The AFM micrographs allowed the observation of PE lamellae with lengths of about 25 nm. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2615–2620, 2001     

Highly crosslinked poly(glycidyl methacrylate-co-divinyl benzene) particles by precipitation polymerization

Stable and smooth surface poly(glycidyl metharylate-co-divinylbenzene) (GMA-co-DVB) microspheres composed of various concentrations of DVB from 20 to 90 mol% in acetonitrile medium were prepared without a significant coagulum by precipitation polymerization. The number-average diameter of the microspheres linearly increases from 2.63 to 3.34 μm and the particle size distribution becomes narrower by decreasing the uniformity from 1.10 to 1.02 with the DVB concentration from 20 to 90 mol%. The yield of polymerization increased from 28.9 to 79.7% with the DVB concentration as well. The FT-IR spectrum shows the characteristic peaks at 1725-1650 cm⁻¹ assigned to the confirmation of the polymerization between GMA and DVB. No glass transition temperature and the onset of the thermal degradation temperature at higher temperature indicate that the poly(GMA-co-DVB) is crosslinked; this is evidenced by the swelling ratio measurement relevant to the crosslinking density of the poly(GMA-co-DVB). The swelling test suggested that the poly(GMA-co-DVB) particles would be a core/shell type structure composing of a highly crosslinked DVB rich-phase in the core part and slightly crosslinked GMA rich-phase in the shell part.     

Polyacrylamide-reactive styrene/unsaturated polyester microgel composites

Reactive microgels (RM) were prepared by the copolymerization of styrene and an unsaturated polyester in an emulsion of oil (styrene + unsaturated polyester) in water. The adsorption of the unsaturated polyester on the water–oil interface ensured the stability of the emulsion. Furthermore, polyacrylamide (PAAM) crosslinked with RM was obtained by suspending RM particles in an aqueous AAM solution and polymerizing the system at 70°C to obtain a PAAM–RM composite. The extraction experiments of the RM with dioxane and of the PAAM with water indicated the presence of small amounts of soluble PAAM homopolymers and negligible amounts of free RM, the materials being PAAM crosslinked by RM. The extent of swelling of these materials in water decreased with increasing weight ratio of RM/AAM and was independent of the composition of RM. When the final polymerization temperature was increased to 130°C, RM reacted not only with AAM to form a crosslinked polymer, but also with itself to form semi-interpenetrating reactive polymer networks (SIRPN). The extent of swelling of PAAM–RM SIRPN in water was much lower than that of the PAAM–RM material. Membranes were also prepared by hot pressing at 200°C the PAAM–RM and PAAM–RM SIRPN composites. The swelling behavior of these membranes in water, acetone, tetrahydrofuran, acrylic acid, ethyl alcohol, and dioxane, as well as in the mixtures of ethyl alcohol–water, acetone–water, tetrahydrofuran–water, and acrylic acid–water, was investigated. © 1995 John Wiley & Sons, Inc.     

UV and corrosion protective behavior of polymer hybrid coating on mild steel

Poly[(pyridine‐4‐yl‐methyl)methacrylate‐co‐butyl methacrylate] [poly(PyMMA‐co‐BMA)] and its ZnO nanocomposites [poly(PyMMA‐co‐BMA)/ZnO] were coated on the mild steel substrate (MS) to improve the corrosion resistance by blocking the destructive ultraviolet radiation (UV‐radiation) and corrosive ions as well. The optical and anticorrosive properties of poly(PyMMA‐co‐BMA) and poly(PyMMA‐co‐BMA)/ZnO (1.0, 1.5, and 2.5 wt %) coatings were evaluated. The surface characterization techniques like UV visible spectroscopy and scanning electron microscope were taken to confirm the formation of poly(PyMMA‐co‐BMA) and poly(PyMMA‐co‐BMA)/ZnO (2.5 wt %) coating on MS. The optical studies revealed that the poly(PyMMA‐co‐BMA)/ZnO (2.5 wt %) coating displays excellent UV blocking properties than other nanocomposite coatings (1.0 and 1.5 wt %). The potentiodynamic polarization and electrochemical impedance spectroscopy studies show that the poly(PyMMA‐co‐BMA) and poly(PyMMA‐co‐BMA)/ZnO (1.0, 1.5, and 2.5 wt %) coated MS in 3.5% (w/v) NaCl provides better protection against corrosion. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46175.     

The Removal of Textile Dyes with Cross-Linked Chitosan-Poly(acrylamide) Adsorbent Hydrogels

This study examined the behaviors and mechanisms of chitosan (CS)-poly(acrylamide) (PAAM) full interpenetrating polymeric network (IPN) hydrogels as an adsorbent to remove EY-4GL and S-Blue textile dyes from an aqueous solution. CS-PAAM IPN hydrogels were prepared by acrylamide monomer polymerization in the presence of a natural polymer, e.g., chitosan. N,N′-methylenebisacrylamide (MBAM) and glutaraldehyde (GLA) were selected to cross-link PAAM and CS chains and a full-IPN structure formed simultaneously. Kinetic swelling studies of CS-PAAM IPNs were carried out with deionized water and aqueous dye solutions. The experimental data clearly suggested that the swelling process obeys second-order kinetics. Network and diffusion parameters for CS-PAAM and PAAM hydrogels were calculated and it was observed that these IPN hydrogels have high cross-linking efficiencies in comparison to PAAM hydrogels. Adsorption of textile dyes onto hydrogels was studied by a batch adsorption technique at 23°C and 40°C, and it was seen that the higher temperature increased the dye adsorption onto the hydrogels. L type (Lan gmuir) adsorption isotherms, according to Giles classification system, were established at the end of adsorption experiments. The prepared IPN hydrogels show good ability to uptake textile dyes from wastewater.     

Synthesis of pH-sensitive hollow polymer microspheres and their application as drug carriers

The pH-sensitive hollow poly(N,N′-methylene bisacrylamide-co-methacrylic acid) (P(MBAAm-co-MAA)) microspheres were prepared by a two-stage distillation precipitation polymerization to afford a core-shell poly(methacrylic acid)/poly(N,N′-methylene bisacrylamide-co-methacrylic acid) (PMAA/(P(MBAAm-co-MAA))) microsphere with subsequent removal of poly(methacrylic acid) (PMAA) core. PMAA/P(MBAAm-co-MAA) core-shell microspheres were synthesized by the second-stage copolymerization of N,N′-methylene bisacrylamide (MBAAm) as crosslinker and the functional methacrylic acid (MAA) comonomer in acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator. The pH-responsive properties of hollow P(MBAAm-co-MAA) microspheres were investigated by dynamic laser scattering (DLS). The loading and controlled-release behavior of the drug for hollow P(MBAAm-co-MAA) microspheres was strongly dependent on the pH values with doxorubicin hydrochloride (DXR) as a model molecule. The core-shell and hollow polymer microspheres were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), DLS and elemental analysis.     

Preparation and characterization of a positive thermoresponsive hydrogel for drug loading and release

A positive thermoresponsive hydrogel composed of poly(acrylic acid)‐graft‐β‐cyclodextrin (PAAc‐g‐β‐CD) and polyacrylamide (PAAm) was synthesized with the sequential interpenetrating polymer network (IPN) method for the purpose of improving its loading and release of drugs. The structure and properties of the PAAc‐g‐β‐CD/PAAm hydrogel (IPN hydrogel) were characterized with Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and swelling measurements. FTIR studies showed that the IPN hydrogel was primarily composed of an IPN of PAAc‐g‐β‐CD and PAAm. The data from DSC and swelling measurements indicated that the phase‐transition temperature or upper critical solution temperature (UCST) of the IPN hydrogel was approximately 35°C. Through the measurement of the temperature dependence of the swelling, increases in the UCST and non‐sensitivity to changes in the salt concentration were observed for the IPN hydrogel versus the normal IPN hydrogel poly(acrylic acid)/PAAm (without β‐cyclodextrin). Furthermore, the swelling/deswelling kinetics of the IPN hydrogel also exhibited an improved controllable response rate versus the normal IPN hydrogel. Ibuprofen (IBU) was chosen as the model drug for examining loading and release from the IPN hydrogel. The experimental data proved that the IPN hydrogel provided a positive drug release pattern; the IBU released faster at 37°C than at 25°C, and improved drug loading and controlled release were achieved by the IPN hydrogel versus the normal IPN hydrogel. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of polymer/silica/polymer tri-layer hybrid materials and the corresponding hollow polymer microspheres with movable cores

Tri-layer poly(methacrylic acid-co-ethyleneglycol dimethacrylate)/silica/poly(ethyleneglycol dimethacrylate) (P(MAA-co-EGDMA)/SiO₂/PEGDMA) and P(MAA-co-EGDMA)/SiO₂/polydivinylbenzene hybrid microspheres were prepared by distillation precipitation polymerization of ethyleneglycol dimethacrylate (EGDMA) and divinylbenzene (DVB) in the presence of 3-(methacryloxy)propyl trimethoxysilane (MPS)-modified P(MAA-co-EGDMA)/SiO₂ microspheres as the seeds. The polymerization of EGDMA and DVB was performed in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator to coat the MPS-modified P(MAA-co-EGDMA)/SiO₂ seeds through the capture of EGDMA and DVB oligomer radicals with the aid of vinyl groups on the surface of modified seeds in the absence of any stabilizer or surfactant. Monodisperse P(MAA-co-EGDMA)/SiO₂ core-shell microspheres were synthesized by coating of a layer of silica onto P(MAA-co-EGDMA) microspheres via a sol-gel process, which were further grafted by MPS incorporating the reactive vinyl groups onto the surface to be used as the seeds for the construction of hybrid microspheres with tri-layer structure. Hollow poly(ethyleneglycol dimethacrylate) (PEGDMA) and poly(divinylbenzene) (PDVB) microspheres with movable P(MAA-co-EGDMA) core were subsequently developed after the selective etching of the silica mid-layer from the tri-layer hybrid microspheres in hydrofluoric acid. The morphology and structure of the tri-layer polymer hybrids and the corresponding hollow polymer microspheres with movable P(MAA-co-EGDMA) core were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra and X-ray photoelectron spectroscopy (XPS).     

Preparation of poly[dl-lactide-co-glycolide]-based microspheres containing protein by use of amphiphilic diblock copolymers of depsipeptide and lactide having ionic pendant groups as biodegradable surfactants by W/O/W emulsion method

To develop the preparative method for poly(dl-lactide-co-glycolide)-based microspheres containing proteins, we prepared microspheres from mixture of poly(dl-lactide-co-glycolide) and polydepsipeptide-block-poly(dl-lactide) having cationic or anionic pendant groups. Since the latter amphiphilic copolymers consisting of hydrophobic poly(dl-lactide) segment and hydrophilic polydepsipeptide segment with amino or carboxyl groups could be converted to cationic or anionic block copolymers, they could act as biodegradable surfactants on the preparation of poly(dl-lactide-co-glycolide)-based microspheres by water-in-oil-in-water emulsion method. The amphiphilic block copolymers were established to stabilize primary emulsions on the preparation of microspheres by scanning electron microscopy. We investigated the effects of the addition of the block copolymers on the entrapment efficiency of protein, the release behavior of protein from microspheres and the stability of protein.     

Poly(vinyl alcohol) Based pH Responsive Semi-IPN Hydrogels: A Comparative Swelling Investigation

The semi-interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) (PVA) and random copolymers of poly(acrylamide-co-sodium methacrylate), poly(AAm-co-NMA); poly(acrylamide-co-potassium methacrylate), poly(AAm-co-KMA); poly(acrylamide-co-maleic acid), poly(AAm-co-MA) were prepared by conventional co-polymerization employing ammonium persulphate (APS)/N,N,N¹,N¹-tetraethylmethylenediamine (TMEDA) as redox initiating system in presence of N,N¹-methylenebisacrylamide (MBA) as a crosslinker. The swelling behavior of these semi-IPN hydrogels were compared in detail in various swelling media, including different pH, salt, and biological fluids.     

Synthesis of silver/polymer colloidal composites from surface-functional porous polymer microspheres

This study presents a different colloidal silver (Ag)/polymer system where Ag nanoparticles are deposited uniformly onto surface-functional porous poly(ethylene glycol dimethacrylate-co-acrylonitrile) (poly(EGDMA-co-AN)) microspheres. The formation and morphology of the composite microspheres were characterized from electron microscopy and X-ray diffraction analyses. The significance of the present report is that owing to the high affinity between Ag and nitrile group (CN) on the large surface of the microspheres, the Ag nanoparticles having a face-centered cubic phase were incorporated evenly into the deep pores of the microspheres with fine size and size distribution. In the preservation test, the Ag/poly(EGDMA-co-AN) composite microspheres obtained showed an excellent anti-bacterial performance, elucidating a high applicability for a new preservative.     

Preparation of magnetite and tumor dual-targeting hollow polymer microspheres with pH-sensitivity for anticancer drug-carriers

The hollow poly(N,N′-methylenebisacrylamide-co-methacrylic acid) (P(MBAAm-co-MAA)) microspheres were prepared by the selective removal of poly(methacrylic acid) (PMAA) core from the corresponding PMAA/P(MBAAm-co-MAA) core-shell microspheres, which were synthesized via a two-stage distillation precipitation polymerization. The magnetic Fe₃O₄ nanoparticles onto the surface of hollow P(MBAAm-co-MAA) microspheres via partial oxidation of ferrous salt during the chemical deposition in the presence of potassium nitrate as oxidant with the aid of hexamethylene tetramine and the magnetic hollow microspheres were further functionalized with folic acid (FA) via the chemical linkage with amino groups of 3-aminopropyl triethoxysilane (APS)-modified P(MBAAm-co-MAA)@Fe₃O₄ microspheres to afford the magnetite and tumor dual-targeting hollow microspheres. The resultant dual-targeting hollow polymer microspheres with pH-sensitivity were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared-spectrometer (FT-IR), UV-vis absorption spectroscopy, and vibrating sample magnetometer (VSM). Finally, the drug loading capacities of the magnetite and tumor dual-targeting hollow P(MBAAm-co-MAA) microspheres and their releasing dependence on pH values were investigated with doxorubicin hydrochloride (DXR) as an anticancer drug model.     

Characterization of cationic water-soluble polyacrylamides

Copolymers of poly(acrylamide-co-acryloyloxyethyltrimethylammonium chloride or AM–CMA) and poly(acrylamide-co-methacryloyloxyethyltrimethylammonium chloride or AM–CMA) prepared by inverse emulsion polymerization were characterized by different analytical techniques. The chemical composition of the copolymers was estimated by elemental analysis and by nuclear magnetic resonance spectroscopy (NMR). NMR spectroscopy and computer simulation were further used for investigating the polymers' sequence distribution. The poly(AM–CMA) copolymers are chemically more homogeneous than are the poly(AM–CMA). The configurational propagation of dyads and triads for the homopolymers obeys Bernouilli's statistics. For the copolymers, the chemical sequences distribution is governed by Markov's first-order statistics.