Encapsulation of a Fragrance via Miniemulsion Polymerization for Temperature‐Controlled Release

The encapsulation of the hydrophobic fragrance 1,2‐dimethyl‐1‐phenyl‐butyramide (DMPBA), a typical C9 amide, in poly(methyl methacrylate), polystyrene, or acrylic copolymer nanoparticles can easily be obtained using a one‐step miniemulsion process. It is shown that this hydrophobic compound directly influences the kinetics, the molecular weight, and the morphology of the nanocapsule formation. The release behavior can be tuned by the temperature in relation to the T_g of the polymer which makes these nanocapsules interesting candidates for temperature‐dependent delivery systems.

     

Facile Phase‐Separation Approach to Encapsulate Functionalized Polymers in Core–Shell Nanoparticles

Core–shell nanoparticles filled with a reactive hydrophobic azide‐terminated polyisobutylene are prepared by a combination of miniemulsion and solvent evaporation techniques. Successful encapsulation is achieved by the rational selection of the polymer pair that displays a large difference in solubility parameters (δ) and interfacial tensions with water (γ_{polymer/water}). By labeling the two polymers with different fluorescent dyes, core–shell structures can be visualized by fluorescence microscopy. After extraction of the polymer present in the core, hollow morphologies are observed by transmission electronic microscopy. The encapsulation efficiency of the reactive polymer increases with decreasing surfactant concentration, with values as high as 90%. This study presents a simple and reaction‐free method to encapsulate reactive polymers. Considering the drawbacks of self‐healing agents with low molar mass, such as volatility and higher propensity for leakage from nanocapsules, the encapsulation of reactive polymers in nanocontainers is an interesting and new alternative for self‐healing materials.

     

Encapsulation of High Biocompatible Hydrophobe Contents in Nonionic Nanoparticles by Miniemulsion Polymerization of Vinyl Acetate or Styrene: Influence of the Hydrophobe Component on the Polymerization

Summary: Encapsulation of hydrophobic compounds in non ionic nanoparticles can easily be performed directly by miniemulsion polymerization of vinyl acetate or styrene with Pluronic F68 as nonionic surfactant and AIBN as initiator. Triglycerides from fatty acid (Miglyol®) or mixture of benzyl benzoate and oligocaprolactones have been used as the hydrophobe component in order to get biocompatible systems. Latexes containing 50% organic phase have been obtained with up to 50% Mygliol engulfed in the nanoparticles. The influence of these hydrophobic compounds on kinetics and molecular weight distribution has been investigated, emphasizing a particular behavior with each one of the two different monomers and compared with the classical hexadecane.

     

Accurate Elemental Analysis of Metal‐Containing Polymer Latexes Using ICP‐Optical Emission Spectrometry

The use of ICP‐OES to determine the metal content of metal‐complex‐containing colloidal dispersions is explored. Colloidal dispersions containing a defined amount of metal complex were produced by miniemulsion polymerization. It was found that simple ICP‐OES measurements yielded apparent metal concentrations significantly below the expected value. To examine the behavior of the colloidal dispersions in the ICP spectrometer, a systematic study on measurement conditions was performed. It was found that the addition of a surfactant to both colloidal dispersions and standards led to measured metal contents close to the theoretical value. Most reliable results were obtained using SDS in concentrations above the cmc.

     

Tunable Morphology and Hydrophobicity of Polyfluoroacrylate/Clay Nanocomposite Prepared by In Situ RAFT Polymerization in Miniemulsion

This investigation reports preparation of polyfluoroacrylate/clay nanocomposite with armored and encapsulated morphology via in situ reversible addition–fragmentation chain transfer (RAFT) polymerization in miniemulsion. In this case, 2,2,3,3,4,4,4‐heptafluoro butyl acrylate (HFBA) is polymerized in miniemulsion in the presence of sodium montmorillonite (NaMMT) using 2‐cyanopropyl dodecyl trithiocarbonate (CPDTC) as a RAFT agent. Gel permeation chromatography (GPC) analysis shows that the polymers have controlled molecular weights as well as narrow dispersity (? ≈ 1.1). The morphology of nanoclay can be tuned by varying the interaction with different functional comonomers. Nanoclay is encapsulated and intercalated in presence of poly (ethylene glycol) methyl ether methacrylate (PEGMEMA) as comonomer. Addition of 2‐acryloxy ethyl trimethyl ammonium chloride (AETAC) as functional comonomer leads to exfoliation of nanoclay resulting armored morphology, as evidenced by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyses. Poly(2,2,3,3,4,4,4‐heptafluoro butyl acrylate) (PHFBA) armored with nanoclay shows improved thermal stability and water resistance.

     

Synthesis of MDMO‐PPV Nanoparticles Via In Situ Sulfinyl Precursor Route Polymerization in Miniemulsion

A facile route to synthesize poly[(2‐methoxy‐5‐(3′,7′,‐dimethyloctyloxy))‐1,4‐phenylene vinylene] polymer nanoparticles (NPs) using the miniemulsion technique in combination with the sulfinyl precursor route polymerization is presented. The reaction conditions involving high temperature are overcome by using ethylene glycol as a polar continuous phase. Particles can be easily transferred into the water phase without the need for additional surfactant. The characteristic UV–vis absorption and the strong fluorescence exhibited by the polymer along with the molecular weight obtained prove the success of the synthetic strategy. Such in situ synthesis of PPV in the form of NPs can be extended to other conjugated polymers, opening new doors for synthesizing luminescent NPs that have tremendous potential in biomedicine and printable electronics.

     

One‐Pot Preparation of Core–Shell,Organic–Inorganic,Hybrid Latexes by In Situ Nanoparticle Precipitation in Pickering Emulsion Polymerization

A one‐pot emulsion polymerization process to produce silica nanoparticles fixed on polymer particles is presented. Simultaneous nanoparticle formation/monomer emulsification and later polymerization of monomers prevent the agglomeration of silica particles and result in hybrid organic–inorganic, core–shell latexes. The emulsion polymerization of methyl methacrylate is performed using nascent silica nanoparticles, cetyltrimethylammonium bromide, and ammonium persulfate as Pickering surfactant, cosurfactant, and initiator, respectively. The effects of parameters like temperature, initiator type and concentration, and cosurfactant and silica precursor amounts on the polymerization, coagulation percentage, and morphology of hybrid particles are determined using SEM and TEM.     

Fabrication of Nanoparticle/Polymer Composites by In Situ Bubble‐Stretching and Reactive Compatibilization

Summary: A new route for fabricating polymer nanocomposites is proposed which combines in situ bubble‐stretching and reactive compatibilization techniques. That is, a polymeric foaming agent p‐vinylphenylsulfonylhydrazide was synthesized and grafted onto nano‐SiO₂. Then, the grafted nanoparticles were melt mixed with matrix PP. In the meantime, some of the side sulfonyl hydrazide groups on the grafted polymer were gasified to form polymer bubbles, leading to rapid inflation of the surrounding matrix that pulled apart the agglomerated nanoparticles, while the remaining non‐decomposed sulfonyl hydrazide groups reacted with the epoxide groups of PGMA‐grafted PP forming chemical bonds. Owing to the simultaneously improved dispersion of the nanoparticles and the interfacial interaction, the mechanical properties, especially notched impact strength, of the nano‐SiO₂/PP composites were greatly enhanced. The structure‐property relationship was carefully studied.

Simultaneous improvement of dispersion nanoparticles and interfacial interaction.     

Synthesis of Multiresponsive Gold@Polymer-Nanohybrid Materials Using Polymer Precursors Obtained by Photoiniferter RAFT Polymerization

Combining gold nanoparticles (GNP) with stimuli-responsive polymers is a fascinating field for applications as sensor materials or in biomedical applications. The synthesis of multiresponsive Au@Polymer hybrid systems in an in situ approach using tailor-made poly(2-(dimethylamino)ethyl methacrylate) (P(DMAEMA)) precursor synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization is introduced. In particular, because of its multiresponsive behavior, P(DMAEMA) is of great interest and is used as the precursor for the synthesis. For the polymerization of the precursor, an approach is introduced that applies the photoiniferter RAFT (photoRAFT) mechanism applicable for tertiary amine-bearing methacrylic monomers like DMAEMA. By varying the chain transfer agents (CTA), the influence of different RAFT Z-groups on the solubility of the Au-hybrids is studied. Aging effects are observed by transmission electron microscopy (TEM) analyses. A comprehensive dynamic light scattering (DLS) study reveals the thermoresponsive behavior of the Au-hybrids in an aqueous solution. The influence of free polymer in solution on the suspension stability is observed. The capability of crosslinking using 1,5-dibromopentane (DBP) and the CO₂ sensitivity of the synthesized hybrids expands the area of their potential application.     

Formation of Inorganic/Organic Nanocomposites by Nitroxide‐Mediated Polymerization in Bulk Using a Bimolecular System

Summary: A series of organic‐inorganic nanoparticles were synthesized by nitroxide‐mediated polymerization (NMP) of butyl acrylate initiated by a self‐assembled monolayer of an azo initiator. The azo initiator was immobilized on silica particles in the presence of a stable nitroxide radical, SG1 (an acyclic β‐phosphonylated nitroxide, N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethyl)propyl nitroxide). After preliminary qualitative characterization by X‐ray spectroscopy (XPS) and Fourier‐transform infrared (FTIR) measurements, the nanoparticles were studied by thermogravimetric analysis (TGA) to determine the polymer grafting density and to permit a comparison with corresponding values of the initiator monolayer. It was demonstrated that the grafting from polymerization exhibits a controlled character with a low polydispersity ( < 1.2) in a large range of molecular weights of the grafted chains (from 4 000 up to 145 000 g · mol^?1) under the conditions when the stable radical SG1, acting as chain growth moderator tethered to the inorganic core, was used.

     

In Situ Spectroelectrochemical Study of Positively and Negatively Charged States in a Donor/Acceptor EDOT/Benzotriazole‐Based Polymer

Positively and negatively charged states in cPBEBT, which consists of EDOT/benzotriazole/EDOT as the building block, are studied using CV, in situ UV‐Vis, and FTIR‐ATR spectroscopy. The results show that cPBEBT is an ambipolar D‐A‐type polymer capable of conducting both holes and electrons. The injected positive and negative charges are distributed over the whole polymer backbone, which is proven by in situ FTIR‐ATR where spectral signatures associated with the benzotriazole unit are observed in both p‐ and n‐doped cPBEBT. HOMO and LUMO values obtained from CV and FTIR‐ATR experiments during oxidation and reduction are compared. cPBEBT is an example of the D‐A approach towards the improvement of the electronic properties of the resultant polymer.     

In Situ Fabrication of Nano-hydroxyapatite in a Macroporous Chitosan Scaffold for Tissue Engineering

A chitosan (CS)/hydroxyapatite (HAP) nanohybrid scaffold with high porosity and homogeneous nanostructure was fabricated through a bionic treatment combined with thermally-induced phase separation. The nano-HAP particles were formed in situ in the scaffold at room temperature instead of mechanically mixing the powders with the polymer component. The scaffold was macroporous with a pore size of about 100–136 μm. The nano-sized HAP particles with diameters of 90–200 nm were scattered homogeneously in the interactively connective pores. Both the improvement of the compressive modulus and yield strength of the scaffolds showed that the in situ nano-HAP particles reinforced the microstructure of the scaffold. The in vitro bioactivity study carried out in simulated body fluid (SBF) indicated good mineralization activity. The crystallization phenomenon suggested that the nano-HAP particles have positive impacts on directing apatite crystallization in the scaffold and led to the good bioactivity of the nanohybrid scaffold.     

Formation of Well‐Defined Polymer Particles in the Sub‐100 nm Size Range by Using Amphiphilic Block Copolymer Surfactants and a Microemulsion Approach

Here, the formation of nanoparticles based on a microemulsion approach and the use of polymer surfactants are described. Therefore, two amphiphilic poly(2‐oxazoline) block copolymers P1 and P2 with alkyne groups in their hydrophobic block have been synthesized by ring‐opening, cationic polymerization. The polymers P1 and P2 are employed in a microemulsion process to stabilize the particle core by core cross‐linking of 1,6‐hexanediol diacrylate (HDDA) using either AIBN as azo‐initiator or 2‐propanethiol as a photo‐initiator for the polymerization reaction. The results show that particle size can be controlled by sonication time, the hydrophilic–hydrophobic balance of the polymer surfactant, and the ratio of polymer surfactant versus HDDA giving access to water‐soluble nanoparticles in a size range of 10–70 nm.

     

In Situ Nuclear Morphology Measurements Using Light Scattering as Biomarkers of Neoplastic Change in Animal Models of Carcinogenesis

Light scattering spectroscopy measurements can be used to determine the structure of tissue samples. Through refined data acquisition and signal processing techniques, quantitative nuclear morphology measurements may be obtained from light scattering data. These data have been used primarily as a biomarker of neoplastic change in a wide range of settings. Here, we review the application of light scattering to assessing the health status of tissues drawn from animal models of carcinogenesis, in particular, the rat esophagus and the golden Syrian hamster trachea carcinogenesis models. In addition, we present results from ex vivo human tissues to demonstrate the relevance of the use of animal models which are excellent surrogates for several human cancers. These models provide the opportunity to develop biomarkers and test chemopreventive and therapy strategies before application in humans.     

Role of Self‐Polarization in a Single‐Step Controlled Synthesis of Linear and Branched Polymer Nanoparticles

In this work, the synthesis of linear (with high aspect ratio) and branched polymer nanoparticles (Nps) via single‐step nanoassembly in a semi‐microfluidic platform is reported. The shape‐controlled synthesis of polymeric material at nanometer scale level remains challenging due to their amorphous or semicrystalline nature. A key to success of this strategy to obtain the compact linear and branched shape of polymer Nps in a single‐step is the use of appropriate concentration of polyelectrolyte molecules in the aqueous phase, and microfluidic technique due to their advantages for providing precise mixing, efficient volume transfer, emulsification, and very homogeneous reaction conditions. The in situ nanoassembly of growing polymer Nps at critical stages during the ongoing polymerization obviously depends on the number of electrical charges supplied by accessible polyelectrolyte that is explained here in detail. The impacts of the different parameters such as concentration of polyelectrolytes, their chain‐lengths, volume ratios, flow rate ratios, and so forth, have been systematically investigated in order to obtain linear and branched polymer nanoparticles.

     

Single‐Step Magnetic Patterning of Iron Nanoparticles in a Semiconducting Polymer Matrix

Summary: A cost‐effective chemical synthesis and single‐step magnetic patterning of iron nanoparticles (size ≈100 nm) in a semiconducting P3OT polymer matrix is reported wherein Fe nanostructures (≈150 ± 50 nm) are periodically aligned with π‐conjugated P3OT chains to form a nanomagnet‐semiconductor‐nanomagnet (Fe‐π‐Fe) structure. The resultant periodic patterning has been characterized by XRD, SEM and AFM techniques and is attributed to the intrinsic alignment of Fe at the nanometer‐scale level in a conjugated polymer matrix under the influence of a magnetic field. Such a P3OT/Fe matrix may find application in magnetic memory devices.

AFM image in nanometers showing the periodic nanostructuring of P3OT‐Fe matrices when the P3OT‐Fe nanocomposite films were grown under an applied magnetic field.     

Preparation of Soft Microactuators in a Continuous Flow Synthesis Using a Liquid‐Crystalline Polymer Crosslinker

We present the synthesis of a polymeric liquid crystalline (LC) crosslinker and its usage in the preparation of soft microactuators. The microactuators, composed of thermoresponsive liquid crystalline elastomers (LCE), are fabricated in a microfluidic device in a continuous “on the fly” process. The LC polymer crosslinker is miscible with the LC monomer and provides for a rapid polymerization and crosslinking. Most importantly, it promotes an enantiotropic mesophase of the mobile monomer phase, which is not provided by conventional nonmesogenic crosslinkers. This allows an isothermal handling inside the microfluidic setup. Temperature‐driven shape changes up to 65% could be achieved by judiciously optimizing the crosslinking density of the LCE particles.     

Stabilization in Water of Polymer/Cu2+ Complexes Using Poly(sodium acrylate)‐graft‐poly(N,N‐dimethylacrylamide) Graft Copolymers

The formation of complexes between Cu²⁺ ions and graft copolymers built from a PANa backbone and non‐ionic hydrophilic PDMAM side chains is investigated by means of turbidimetry, viscometry, DLS, ζ‐potential measurements, and UV‐vis spectrophotometry. The macroscopic phase separation which accompanies complexation is gradually depressed with increasing PDMAM content x, and water‐soluble complexes are formed for x = 70 mol‐%. The polymer/Cu²⁺ complexation is a charge neutralization process that leads to the formation of water‐soluble, compact, hybrid polymer/metal ion nanostructures. UV‐vis data indicate that this graft copolymer could possibly serve as a water‐soluble sensor for Cu²⁺ ions.

     

Patterned Immobilization of a Luminescent Ru(II) Complex in Polymer Films Using the Photoreaction of Benzyl thiocyanate: Toward Color Emission Tuning of Electroluminescent Devices

This contribution deals with the patterned immobilization of a highly luminescent Ru(II) complex in thin polymer films. Photosensitive polymers bearing benzyl thiocyanate groups in the side chain undergo a photoisomerization reaction upon irradiation with UV light. This photoreaction leads to the formation of isothiocyanate groups, which readily react with primary amino groups. We report on the immobilization of a highly luminescent Ru(II) complex in the illuminated areas of a norbornene based polymer by means of this photoreaction. In combination with lithographic techniques, patterned, luminescent polymer films are realized. A novel approach for tuning the electroluminescence of polyfluorene‐based organic light‐ emitting diodes by the immobilization of this Ru(II) complex in the emission layer is suggested.