Synthesis of Highly Monodisperse Surface-Functional Microspheres by Photoinitiated RAFT Dispersion Polymerization Using Macro-RAFT Agents

Highly monodisperse PMMA microspheres have been synthesized by photoinitiated RAFT dispersion polymerization in the presence of a Macro-RAFT agent and a small molecular RAFT agent. A particle yield of over 90% was achieved within 3 h under UV irradiation at room temperature. The Macro-RAFT agent acts as a stabilizer and stabilizes the particles via formation of block copolymers in situ, and XPS analysis shows that about 29.9% of the particle surface was covered by the stabilizer. Various surface functional microspheres were prepared by using four kinds of Macro-RAFT agents, including poly­(methoxy poly­(ethylene glycol) acrylate)-based trithiocarbonate (P­(mPEGA)-TTC), poly­(methoxy poly­(ethylene glycol) acrylate-<i>co</i>-acrylic acid)-based trithiocarbonate (P­(mPEGA-<i>co</i>-AA)-TTC), poly­(acrylic acid)-based trithiocarbonate (PAA-TTC), and poly­(methoxy poly­(ethylene glycol) acrylate-<i>co</i>-4-vinylpyridine)-based trithiocarbonate (P­(mPEGA-<i>co</i>-4VP)-TTC). Ag/PMMA nanocomposite spheres were prepared using the P­(mPEGA-<i>co</i>-AA)-TTC stabilized microspheres. The PAA-TTC stabilized microspheres showed pH sensitivity. The colloidal stability of the particles prepared by this photoinitiated RAFT dispersion polymerization was also investigated

Phototriggered Base Proliferation: A Highly Efficient Domino Reaction for Creating Functionally Photo-Screened Materials

Phototriggered base proliferation as a highly efficient domino reaction is presented for creating functionally photo-screened materials, providing a strategy for the photopolymerization of shadow areas via chemically diffuse amines toward the nonirradiated areas during polymerization. By integrating proliferated amines with a peroxide initiator (dibenzoyl peroxide, BPO), phototriggered self-propagating polymerization of acrylate monomers in three-dimensional space was achieved. The advantages of this approach lie in its enhanced photosensitivity, increased propagating velocity, and elevated double-bond conversion (90%) while reducing the local high temperature and the minimum BPO concentration that sustain a traveling front. Astonishingly, the propagating velocity and local maximum temperature can be well-modulated by varied BPO concentration and the appropriate amount of BA-BPD (1-(9-fluorenylmethoxycarbonyl)-4-benzylpiperidine) concentration, respectively. Finally, functionally photo-screened material containing carbon nanotubes was successfully prepared by phototriggered base proliferation reactions

PMMA Microspheres with Embedded Lanthanide Nanoparticles by Photoinitiated Dispersion Polymerization with a Carboxy-Functional Macro-RAFT Agent

Functional poly­(methyl methacrylate) (PMMA) microbeads with a very narrow size distribution were synthesized by photoinitiated RAFT dispersion polymerization in aqueous ethanol using an acrylic acid–oligo­(ethylene glycol) copolymer as a macro-RAFT agent. These particles are a prototype for multiparameter bead-based assays employing mass cytometry, a technique in which metal-encoded beads are injected into the plasma torch of an inductively coupled plasma mass spectrometer (ICP-MS), and the metal ions generated are detected by time-of-flight mass spectrometry. To label the beads, the polymerization reaction was carried out in the presence of various types of small (ca. 5 nm) lanthanide fluoride (LnF₃) nanoparticles (e.g., LaF₃, CeF₃, and TbF₃) with polymerizable methacrylate groups on their surface. The type of metal ion and the metal content of the PMMA microbeads could be varied by changing the composition of the reaction medium. An important feature of these microbeads is that acrylic acid groups in the corona are available for covalent attachment of biomolecules. As a proof of concept, FITC–streptavidin (FITC-SAv) was covalently coupled to the surface of a Ln-encoded microbead sample. The number of FITC-SAv binding sites on the beads was determined through three parallel assays involving biotin derivatives. Interaction of the beads with a biotin–tetramethylrhodamine derivative was monitored by fluorescence, whereas interaction of the beads with a biotin-DOTA-Lu derivative was monitored both by ICP-MS and by mass cytometry. Each measurement detected an average of ca. 5 × 10⁴ biotins per microsphere. Control experiments with beads covalently labeled with FITC–bovine serum albumin (FITC-BSA) showed only very low levels of nonspecific binding

Synthesis of PMMA Microparticles with a Narrow Size Distribution by Photoinitiated RAFT Dispersion Polymerization with a Macromonomer as the Stabilizer

Macromonomers can serve as efficient and effective stabilizers for dispersion polymerization of monomers such as styrene and methyl methacrylate, but the size distributions of the polymer microparticles obtained tend to be broad. We are interested in functional microbeads which can be used for immunoassays, where the size distribution has to be very narrow. We report a photoinitiated RAFT dispersion polymerization of methyl methacrylate (MMA) in ethanol–water mixtures, with methoxy-poly­(ethylene glycol) methacrylate (<i>M</i>_n = 2000 g/mol, EO₄₅) as the reactive steric stabilizer. We identify reaction conditions where one can obtain PMMA microspheres with coefficient of variation in the particle diameter (CV_d) less than 3%. Carboxy-functional PMMA microspheres were obtained by a two-stage (seeded) polymerization with methacrylic acid (MAA) added as a comonomer in the second stage. We show that the functional microspheres prepared in this way are effective substrates for the covalent attachment of proteins such as BSA and IgG immunoglobulins. In one set of experiments with a dye-labeled secondary antibody, we found that we could detect 10⁴ IgGs per PMMA microbead

Photoinitiated RAFT Dispersion Polymerization: A Straightforward Approach toward Highly Monodisperse Functional Microspheres

A straightforward dispersion polymerization procedure for the synthesis of monodisperse functional polymeric microspheres is proposed in this article. This method overcomes the problems deriving from the highly sensitive nucleation stage by introducing both photoinitiation and a RAFT chain transfer agent to the reaction. The process of the formation and growth of particles in the procedure was investigated and found to be quite different from that in a traditional dispersion polymerization. Various kinds of PMMA-based functional microspheres with high size uniformity were synthesized in a single step by this strategy. The microspheres remained uniform in size, even at concentrations of cross-linker or functional comonomer up to 10 wt %

Pāli Commentaries (Aṭṭhakathā)

<p>Each day (24H) was divided as Period 1(7:00–19:00) and Period 2(19:00–7:00). LD: Period 1 with light of quartz lamp, Period 2 with darkness; LL: continuous illumination by quartz lamp; DD: continuous darkness.</p

Adult Tea Green Leafhoppers, <i>Empoasca onukii</i> (Matsuda), Change Behaviors under Varying Light Conditions

<div><p>Insect behaviors are often influenced by light conditions including photoperiod, light intensity, and wavelength. Understanding pest insect responses to changing light conditions may help with developing alternative strategies for pest control. Little is known about the behavioral responses of leafhoppers (Hemiptera: Cicadellidae) to light conditions. The behavior of the tea green leafhopper, <i>Empoasca onukii</i> Matsuda, was examined when exposed to different light photoperiods or wavelengths. Observations included the frequency of locomotion and cleaning activities, and the duration of time spent searching. The results suggested that under normal photoperiod both female and male adults were generally more active in darkness (i.e., at night) than in light. In continuous darkness (DD), the locomotion and cleaning events in Period 1 (7:00–19:00) were significantly increased, when compared to the leafhoppers under normal photoperiod (LD). Leafhoppers, especially females, changed their behavioral patterns to a two day cycle under DD. Under continuous illumination (continuous quartz lamp light, yellow light at night, and green light at night), the activities of locomotion, cleaning, and searching were significantly suppressed during the night (19:00–7:00) and locomotion activities of both females and males were significantly increased during the day (7:00–19:00), suggesting a shift in circadian rhythm. Our work suggests that changes in light conditions, including photoperiod and wavelength, can influence behavioral activities of leafhoppers, potentially affecting other life history traits such as reproduction and development, and may serve as a method for leafhopper behavioral control.</p></div

Comparison of the three behavioral values of <i>E</i>. <i>onukii</i> in total ten days’ observation in different light wavelength treatments, during Period 1and Period 2 using a two way ANOVA.

<p>Comparison of the three behavioral values of <i>E</i>. <i>onukii</i> in total ten days’ observation in different light wavelength treatments, during Period 1and Period 2 using a two way ANOVA.</p

Total amount of the three behaviors, locomotion, cleaning and searching activities, for the 10 days during Period 1 (left side) or Period 2 (center) of <i>E</i>. <i>onukii</i> males and females total ratio in Period 2 (Period 1 / (Period 1 + Period 2), right side), under varying wavelength treatments.

<p>Significant differences among the three treatments are marked with different letters (LSD, <i>P</i><0.05, females marked with lowercase letters, males marked with capital letters).</p

System used for leafhopper behavior observations.

<p>A: observation room; B: infrared camera (two in total, the figure shows one); C: door; D: observation window (hollow glass); E: deadening felt (inside the room); F: copper mesh; G: composite board; H: sound proof cotton; I: plastic wrap (with ventholes); J: glass tube B (10mm in diameter, 100mm in high); K,S: tested leafhopper; L: tea tip; M: cotton; N: glass tube B.</p