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A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (31 January 2016) | Viewed by 109933

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Prof. Dr. Guanghui Ma

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Guest Editor

State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
Interests: bioseparation media; carrier for drug controlled release; particle adjuvant for vaccine; hydrogel; polymer modification of biodrugs

Prof. Dr. Haruma Kawaguchi

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Guest Editor

1. Research Institute of Engineering, Kanagawa University, Yokohama, 221-8686, Japan
2. Emeritus Professor, Keio University, Japan
Interests: Polymer Chemistry; Polymer Colloid; Soft Matter/Hydro-Gel; Bio-Functional Polymers; Particle-Forming Polymerization

Prof. Dr. To Ngai

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Guest Editor

Department of Chemistry, The Chinese University of Hong Kong, Hong Kong 999077, China
Interests: colloidal particle; interfacial science; polymer and soft materials
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Special Issue Information

Dear Colleagues,

This Special Issue cooperates with the 5^th Asian Symposium on Emulsion Polymerization and Functional Polymeric Microspheres (ASEPFPM 2015) (http://asepfpm5.csp.escience.cn). Polymeric microspheres are basic materials for recent progress in environmental science, architecture, biomedicine, electronics, food, cosmetics, etc. While much progress has been made over the past few decades, there are still big challenges for the preparation of functional particles and the verification of preparation mechanisms; there is much room for growth in our ability to provide for high performance in these areas. The general theme of this symposium is to discuss recent advances in both fundamentals and applications, as well as to promote science and industrialization translation. As a memorial proceeding of the symposium, this Special Issue is published to provide a platform for other academic and industrial scientists and experts from Asian countries to meet, so as to promote potential collaborations. We trust that this issue can be extended more broadly to applications of functional polymer microspheres by exchanging new ideas and needs, especially in new emerging applications. 20% discount of Article Processing Charges is available for all the attendees of ASEPFPM2015.

Prof. Dr. Guanghui Ma
Prof. Dr. Haruma Kawaguchi
Prof. Dr. To Ngai
Guest Editors

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Keywords

Micro/Nano microspheres
Polymerization and characterization
Emulsion
Mechanism
Applications

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Published Papers (12 papers)

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3235 KiB

Open AccessArticle

Aerosol-Assisted Fast Formulating Uniform Pharmaceutical Polymer Microparticles with Variable Properties toward pH-Sensitive Controlled Drug Release

by Hong Lei, Xingmin Gao, Winston Duo Wu, Zhangxiong Wu and Xiao Dong Chen

Polymers 2016, 8(5), 195; https://doi.org/10.3390/polym8050195 - 14 May 2016

Cited by 9 | Viewed by 8057

Abstract

Microencapsulation is highly attractive for oral drug delivery. Microparticles are a common form of drug carrier for this purpose. There is still a high demand on efficient methods to fabricate microparticles with uniform sizes and well-controlled particle properties. In this paper, uniform hydroxypropyl methylcellulose phthalate (HPMCP)-based pharmaceutical microparticles loaded with either hydrophobic or hydrophilic model drugs have been directly formulated by using a unique aerosol technique, i.e., the microfluidic spray drying technology. A series of microparticles of controllable particle sizes, shapes, and structures are fabricated by tuning the solvent composition and drying temperature. It is found that a more volatile solvent and a higher drying temperature can result in fast evaporation rates to form microparticles of larger lateral size, more irregular shape, and denser matrix. The nature of the model drugs also plays an important role in determining particle properties. The drug release behaviors of the pharmaceutical microparticles are dependent on their structural properties and the nature of a specific drug, as well as sensitive to the pH value of the release medium. Most importantly, drugs in the microparticles obtained by using a more volatile solvent or a higher drying temperature can be well protected from degradation in harsh simulated gastric fluids due to the dense structures of the microparticles, while they can be fast-released in simulated intestinal fluids through particle dissolution. These pharmaceutical microparticles are potentially useful for site-specific (enteric) delivery of orally-administered drugs. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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2264 KiB

Open AccessArticle

Co-Assembly of Graphene Oxide and Albumin/Photosensitizer Nanohybrids towards Enhanced Photodynamic Therapy

by Ruirui Xing, Tifeng Jiao, Yamei Liu, Kai Ma, Qianli Zou, Guanghui Ma and Xuehai Yan

Polymers 2016, 8(5), 181; https://doi.org/10.3390/polym8050181 - 4 May 2016

Cited by 116 | Viewed by 9725

Abstract

The inactivation of photosensitizers before they reach the targeted tissues can be an important factor, which limits the efficacy of photodynamic therapy (PDT). Here, we developed co-assembled nanohybrids of graphene oxide (GO) and albumin/photosensitizer that have a potential for protecting the photosensitizers from the environment and releasing them in targeted sites, allowing for an enhanced PDT. The nanohybrids were prepared by loading the pre-assembled nanoparticles of chlorin e6 (Ce6) and bovine serum albumin (BSA) on GO via non-covalent interactions. The protection to Ce6 is evident from the inhibited fluorescence and singlet oxygen generation activities of Ce6–BSA–GO nanohybrids. Importantly, compared to free Ce6 and Ce6 directly loaded by GO (Ce6–GO), Ce6–BSA–GO nanohybrids showed enhanced cellular uptake and in vitro release of Ce6, leading to an improved PDT efficiency. These results indicate that the smart photosensitizer delivery system constructed by co-assembly of GO and albumin is promising to improve the stability, biocompatibility, and efficiency of PDT. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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5089 KiB

Open AccessArticle

The Construction of an Aqueous Two-Phase System to Solve Weak-Aggregation of Gigaporous Poly(Styrene-Divinyl Benzene) Microspheres

by Donglai Zhang, Weiqing Zhou, Juan Li, Yace Mi, Zhiguo Su and Guanghui Ma

Polymers 2016, 8(5), 142; https://doi.org/10.3390/polym8050142 - 26 Apr 2016

Cited by 8 | Viewed by 6029

Abstract

Gigaporous poly(styrene-divinyl benzene) microspheres made via the surfactant reverse micelles swelling method had a controllable pore size of 100–500 nm. These microspheres had unique advantages in biomacromolecule separation and enzymes immobilization. However, the obtained microspheres adhered to each other in the preparation process. Though the weak aggregation could be re-dispersed easily by mechanical force, it will be difficult to scale up. By analyzing the formation mechanism of the aggregates, a method was presented to rebuild the interface between the internal aqueous channel and the external continuous phase by constructing an aqueous two-phase system (ATPS). Based on the ATPS, the method of emulsification, stirring speed, and surfactant concentration in oil phase were optimized. Under the optimum condition (screen emulsification method, 120 rpm for polymerization and 55% surfactant), the microspheres with a controllable particle size of 10–40 μm and a pore size of about 150 nm were obtained. This new method could significantly decrease the weak-aggregation of microspheres. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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2456 KiB

Open AccessArticle

Effect of Small Reaction Locus in Free-Radical Polymerization: Conventional and Reversible-Deactivation Radical Polymerization

by Hidetaka Tobita

Polymers 2016, 8(4), 155; https://doi.org/10.3390/polym8040155 - 20 Apr 2016

Cited by 8 | Viewed by 5376

Abstract

When the size of a polymerization locus is smaller than a few hundred nanometers, such as in miniemulsion polymerization, each locus may contain no more than one key-component molecule, and the concentration may become much larger than the corresponding bulk polymerization, leading to a significantly different rate of polymerization. By focusing attention on the component having the lowest concentration within the species involved in the polymerization rate expression, a simple formula can predict the particle diameter below which the polymerization rate changes significantly from the bulk polymerization. The key component in the conventional free-radical polymerization is the active radical and the polymerization rate becomes larger than the corresponding bulk polymerization when the particle size is smaller than the predicted diameter. The key component in reversible-addition-fragmentation chain-transfer (RAFT) polymerization is the intermediate species, and it can be used to predict the particle diameter below which the polymerization rate starts to increase. On the other hand, the key component is the trapping agent in stable-radical-mediated polymerization (SRMP) and atom-transfer radical polymerization (ATRP), and the polymerization rate decreases as the particle size becomes smaller than the predicted diameter. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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5445 KiB

Open AccessArticle

Towards A Deeper Understanding of the Interfacial Adsorption of Enzyme Molecules in Gigaporous Polymeric Microspheres

by Weichen Wang, Weiqing Zhou, Wei Wei, Juan Li, Dongxia Hao, Zhiguo Su and Guanghui Ma

Polymers 2016, 8(4), 116; https://doi.org/10.3390/polym8040116 - 7 Apr 2016

Cited by 3 | Viewed by 5829

Abstract

Compared with the one immobilized in the conventional mesoporous microspheres, the enzyme immobilized in gigaporous microspheres showed much higher activity and better stability. To gain a deeper understanding, we herein selected lipase as a prototype to comparatively analyze the adsorption behavior of lipase at interfaces in gigaporous and mesoporous polystyrene microspheres at very low lipase concentration, and further compared with the adsorption on a completely flat surface (a chip). Owing to the limited space of narrow pores, lipase molecules were inclined to be adsorbed as a monolayer in mesoporous microspheres. During this process, the interaction between lipase molecules and the interface was stronger, which could result in the structural change of lipase molecular and compromised specific activity. In addition to monolayer adsorption, more multilayer adsorption of enzyme molecules also occurred in gigaporous microspheres. Besides the adsorption state, the pore curvature also affected the lipase adsorption. Due to the multilayer adsorption, the excellent mass transfer properties for the substrate and the product in the large pores, and the small pore curvature, lipase immobilized in gigaporous microspheres showed better behaviors. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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5257 KiB

Open AccessArticle

Green Synthesis of Smart Metal/Polymer Nanocomposite Particles and Their Tuneable Catalytic Activities

by Noel Peter Bengzon Tan, Cheng Hao Lee and Pei Li

Polymers 2016, 8(4), 105; https://doi.org/10.3390/polym8040105 - 23 Mar 2016

Cited by 49 | Viewed by 11008

Abstract

Herein we report a simple and green synthesis of smart Au and Ag@Au nanocomposite particles using poly(N-isopropylacrylamide)/polyethyleneimine (PNIPAm/PEI) core-shell microgels as dual reductant and templates in an aqueous system. The nanocomposite particles were synthesized through a spontaneous reduction of tetrachloroauric (III) acid to gold nanoparticles at room temperature, and in situ encapsulation and stabilization of the resultant gold nanoparticles (AuNPs) with amine-rich PEI shells. The preformed gold nanoparticles then acted as seed nanoparticles for further generation of Ag@Au bimetallic nanoparticles within the microgel templates at 60 °C. These nanocomposite particles were characterized by TEM, AFM, XPS, UV-vis spectroscopy, zeta-potential, and particle size analysis. The synergistic effects of the smart nanocomposite particles were studied via the reduction of p-nitrophenol to p-aminophenol. The catalytic performance of the bimetallic Ag@Au nanocomposite particles was 25-fold higher than that of the monometallic Au nanoparticles. Finally, the controllable catalytic activities of the Au@PNIPAm/PEI nanocomposite particles were demonstrated via tuning the solution pH and temperature. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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4541 KiB

Open AccessArticle

Amphiphilic Fluorinated Block Copolymer Synthesized by RAFT Polymerization for Graphene Dispersions

by Hyang Moo Lee, Suguna Perumal and In Woo Cheong

Polymers 2016, 8(3), 101; https://doi.org/10.3390/polym8030101 - 22 Mar 2016

Cited by 15 | Viewed by 8444

Abstract

Despite the superior properties of graphene, the strong π–π interactions among pristine graphenes yielding massive aggregation impede industrial applications. For non-covalent functionalization of highly-ordered pyrolytic graphite (HOPG), poly(2,2,2-trifluoroethyl methacrylate)-block-poly(4-vinyl pyridine) (PTFEMA-b-PVP) block copolymers were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and used as polymeric dispersants in liquid phase exfoliation assisted by ultrasonication. The HOPG graphene concentrations were found to be 0.260–0.385 mg/mL in methanolic graphene dispersions stabilized with 10 wt % (relative to HOPG) PTFEMA-b-PVP block copolymers after one week. Raman and atomic force microscopy (AFM) analyses revealed that HOPG could not be completely exfoliated during the sonication. However, on-line turbidity results confirmed that the dispersion stability of HOPG in the presence of the block copolymer lasted for one week and that longer PTFEMA and PVP blocks led to better graphene dispersibility. Force–distance (F–d) analyses of AFM showed that PVP block is a good graphene-philic block while PTFEMA is methanol-philic. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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7699 KiB

Open AccessArticle

Preparation of Uniform-Sized and Dual Stimuli-Responsive Microspheres of Poly(N-Isopropylacrylamide)/Poly(Acrylic acid) with Semi-IPN Structure by One-Step Method

by En-Ping Lai, Yu-Xia Wang, Yi Wei and Guang Li

Polymers 2016, 8(3), 90; https://doi.org/10.3390/polym8030090 - 17 Mar 2016

Cited by 28 | Viewed by 8728

Abstract

A novel strategy was developed to synthesize uniform semi-interpenetrating polymer network (semi-IPN) microspheres by premix membrane emulsification combined with one-step polymerization. Synthesized poly(acrylic acid) (PAAc) polymer chains were added prior to the inner water phase, which contained N-isopropylacrylamide (NIPAM) monomer, N,N′-methylene bisacrylamide (MBA) cross-linker, and ammonium persulfate (APS) initiator. The mixtures were pressed through a microporous membrane to form a uniform water-in-oil emulsion. By crosslinking the NIPAM in a PAAc-containing solution, microspheres with temperature- and pH-responsive properties were fabricated. The semi-IPN structure and morphology of the microspheres were confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average diameter of the obtained microspheres was approximately 6.5 μm, with Span values of less than 1. Stimuli-responsive behaviors of the microspheres were studied by the cloud-point method. The results demonstrated that semi-IPN microspheres could respond independently to both pH and temperature changes. After storing in a PBS solution (pH 7.0) at 4 °C for 6 months, the semi-IPN microspheres remained stable without a change in morphology or particle size. This study demonstrated a promising method for controlling the synthesis of semi-IPN structure microspheres with a uniform size and multiple functionalities. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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4387 KiB

Open AccessArticle

Fabrication of Alkoxyamine-Functionalized Magnetic Core-Shell Microspheres via Reflux Precipitation Polymerization for Glycopeptide Enrichment

by Meng Yu, Yi Di, Ying Zhang, Yuting Zhang, Jia Guo, Haojie Lu and Changchun Wang

Polymers 2016, 8(3), 74; https://doi.org/10.3390/polym8030074 - 4 Mar 2016

Cited by 11 | Viewed by 8971

Abstract

As a facile method to prepare hydrophilic polymeric microspheres, reflux precipitation polymerization has been widely used for preparation of polymer nanogels. In this article, we synthesized a phthalamide-protected N-aminooxy methyl acrylamide (NAMAm-p) for preparation of alkoxyamine-functionalized polymer composite microspheres via reflux precipitation polymerization. The particle size and functional group density of the composite microspheres could be adjusted by copolymerization with the second monomers, N-isopropyl acrylamide, acrylic acid or 2-hydroxyethyl methacrylate. The resultant microspheres have been characterized by TEM, FT-IR, TGA and DLS. The experimental results showed that the alkoxyamine group density of the microspheres could reach as high as 1.49 mmol/g, and these groups showed a great reactivity with ketone/aldehyde compounds. With the aid of magnetic core, the hybrid microspheres could capture and magnetically isolate glycopeptides from the digested mixture of glycopeptides and non-glycopeptides at a 1:100 molar ratio. After that, we applied the composite microspheres to profile the glycol-proteome of a normal human serum sample, 95 unique glycopeptides and 64 glycoproteins were identified with these enrichment substrates in a 5 μL of serum sample. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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13824 KiB

Open AccessArticle

Polydopamine Particle as a Particulate Emulsifier

by Nobuaki Nishizawa, Ayaka Kawamura, Michinari Kohri, Yoshinobu Nakamura and Syuji Fujii

Polymers 2016, 8(3), 62; https://doi.org/10.3390/polym8030062 - 26 Feb 2016

Cited by 50 | Viewed by 10297

Abstract

“Pickering-type” emulsions were prepared using polydopamine (PDA) particles as a particulate emulsifier and n-dodecane, methyl myristate, toluene or dichloromethane as an oil phase. All the emulsions prepared were oil-in-water type and an increase of PDA particle concentration decreased oil droplet diameter. The PDA particles adsorbed to oil–water interface can be crosslinked using poly(ethylene imine) as a crosslinker, and the PDA particle-based colloidosomes were successfully fabricated. Scanning electron microscopy studies of the colloidosomes after removal of inner oil phase revealed a capsule morphology, which is strong evidence for the attachment of PDA particles at the oil–water interface thereby stabilizing the emulsion. The colloidosomes after removal of inner oil phase could retain their capsule morphology, even after sonication. On the other hand, the residues obtained after oil phase removal from the PDA particle-stabilized emulsion prepared in the absence of any crosslinker were broken into small fragments of PDA particle flocs after sonication. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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6474 KiB

Open AccessArticle

Improved Stability of Emulsions in Preparation of Uniform Small-Sized Konjac Glucomanna (KGM) Microspheres with Epoxy-Based Polymer Membrane by Premix Membrane Emulsification

by Yace Mi, Juan Li, Weiqing Zhou, Rongyue Zhang, Guanghui Ma and Zhiguo Su

Polymers 2016, 8(3), 53; https://doi.org/10.3390/polym8030053 - 23 Feb 2016

Cited by 7 | Viewed by 11419

Abstract

Uniform small-sized (<10 μm) Konjac glucomanna (KGM) microspheres have great application prospects in bio-separation, drug delivery and controlled release. Premix membrane emulsification is an effective method to prepare uniform small-sized KGM microspheres. However, since KGM solution bears strong alkalinity, it requires the membrane to have a hydrophobic surface resistant to alkali. In this study, uniform small-sized KGM microspheres were prepared with epoxy-based polymer membrane (EP) we developed by premix membrane emulsification. It was found that emulsion coalescence and flocculation occurred frequently due to the high interface energy and sedimentation velocity of KGM emulsions. Emulsion stability had a significant influence on the uniformity and dispersity of the final KGM microspheres. To improve the stability of the emulsions, the effects of the concentration of the emulsifier, the viscosity of the KGM solution, the oil phase composition and the feeding method of epoxy chloropropane (EC) on the preparation results were studied. Under optimal preparation conditions (emulsifier 5 wt % PO-5s, KGM III (145.6 mPa·s), weight ratio of liquid paraffin (LP) to petroleum ether (PE) 11:1), uniform and stable KGM emulsions (d = 7.47 μm, CV = 15.35%) were obtained and crosslinked without emulsion-instable phenomena. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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2857 KiB

Open AccessArticle

Initiator Systems Effect on Particle Coagulation and Particle Size Distribution in One-Step Emulsion Polymerization of Styrene

by Baijun Liu, Yajun Wang, Mingyao Zhang and Huixuan Zhang

Polymers 2016, 8(2), 55; https://doi.org/10.3390/polym8020055 - 19 Feb 2016

Cited by 42 | Viewed by 15221

Abstract

Particle coagulation is a facile approach to produce large-scale polymer latex particles. This approach has been widely used in academic and industrial research owing to its higher polymerization rate and one-step polymerization process. Our work was motivated to control the extent (or time) of particle coagulation. Depending on reaction parameters, particle coagulation is also able to produce narrowly dispersed latex particles. In this study, a series of experiments were performed to investigate the role of the initiator system in determining particle coagulation and particle size distribution. Under the optimal initiation conditions, such as cationic initiator systems or higher reaction temperature, the time of particle coagulation would be advanced to particle nucleation period, leading to the narrowly dispersed polymer latex particles. By using a combination of the Smoluchowski equation and the electrostatic stability theory, the relationship between the particle size distribution and particle coagulation was established: the earlier the particle coagulation, the narrower the particle size distribution, while the larger the extent of particle coagulation, the larger the average particle size. Combined with the results of previous studies, a systematic method controlling the particle size distribution in the presence of particle coagulation was developed. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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