Research

10 pages, 2785 KiB

Open AccessArticle

Phase Separation Driven On-Demand Debondable Waterborne Pressure-Sensitive Adhesives

by Ehsan Mehravar, Michael A. Gross, Gracia Patricia Leal, Bernd Reck, Jose R. Leiza and José M. Asua

Polymers 2018, 10(9), 975; https://doi.org/10.3390/polym10090975 - 02 Sep 2018

Cited by 4 | Viewed by 4149

Abstract

A waterborne pressure-sensitive adhesive (PSA) that shows high adhesive performance and easy debondability on demand without leaving residues on the substrate (adhesive failure) has been developed. A key component of the PSA is a semicrystalline phase that is beneficial for the adhesive properties [...] Read more.

A waterborne pressure-sensitive adhesive (PSA) that shows high adhesive performance and easy debondability on demand without leaving residues on the substrate (adhesive failure) has been developed. A key component of the PSA is a semicrystalline phase that is beneficial for the adhesive properties and that becomes fluid when heated above the melting temperature. Migration of this liquid-like polymer to the substrate-adhesive interface and hardening upon cooling results in a hard non-tacky interface that facilitates debonding. The effect of the particle morphology on the debonding ability is discussed. Full article

(This article belongs to the Special Issue Emulsion Polymerization)

► Show Figures

Graphical abstract

22 pages, 8682 KiB

Open AccessArticle

A Roadmap towards Successful Nanocapsule Synthesis via Vesicle Templated RAFT-Based Emulsion Polymerization

by Wendy Rusli, Alexander W. Jackson and Alexander Van Herk

Polymers 2018, 10(7), 774; https://doi.org/10.3390/polym10070774 - 15 Jul 2018

Cited by 10 | Viewed by 4555

Abstract

Vesicle templated emulsion polymerization is a special form of emulsion polymerization where the polymer is grown from the outside of the vesicle, leading to nanocapsules. Cost effective nanocapsules synthesis is in high demand due to phasing out of older methods for capsule synthesis. [...] Read more.

Vesicle templated emulsion polymerization is a special form of emulsion polymerization where the polymer is grown from the outside of the vesicle, leading to nanocapsules. Cost effective nanocapsules synthesis is in high demand due to phasing out of older methods for capsule synthesis. Although the first indications of this route being successful were published some 10 years ago, until now a thorough understanding of the parameters controlling the morphologies resulting from the template emulsion polymerization was lacking. Most often a mixture of different morphologies was obtained, ranging from solid particles to pro-trusion structures to nanocapsules. A high yield of nanocapsules was not achieved until now. In this paper, the influence of initial vesicle dispersion, choice of the Reversible Addition-Fragmentation chain Transfer (RAFT) species and oligomer, monomer and crosslinker have been investigated. It turns out that good initial vesicle dispersion, molecular control of the RAFT process, a not too hydrophobic monomer and some crosslinking is needed to result in high yield of nanocapsules. In previous work, the level of RAFT control was often suboptimal and not properly verified and although nanocapsules were shown, other morphologies were also present. We now believe we have a full understanding of vesicle templated nanocapsules synthesis, relevant to many applications. Full article

(This article belongs to the Special Issue Emulsion Polymerization)

► Show Figures

Graphical abstract

11 pages, 2725 KiB

Open AccessArticle

Fructose-Based Acrylic Copolymers by Emulsion Polymerization

by Jessica S. Desport, Mónica Moreno and María J. Barandiaran

Polymers 2018, 10(5), 488; https://doi.org/10.3390/polym10050488 - 02 May 2018

Cited by 8 | Viewed by 4438

Abstract

The exploration of a renewable resource for the preparation of waterborne copolymers was conducted. Low molar mass sugar resources were selected for their wide availability. A fructose-based monomer (MF) bearing a methacrylate radically polymerizable group was successfully synthesized. The latter was shown to [...] Read more.

The exploration of a renewable resource for the preparation of waterborne copolymers was conducted. Low molar mass sugar resources were selected for their wide availability. A fructose-based monomer (MF) bearing a methacrylate radically polymerizable group was successfully synthesized. The latter was shown to be able to homopolymerize in emulsion. The high T_g of the resulting polymer (about 115 °C) makes it of particular interest for adhesive and coating applications where hard materials are necessary to ensure valuable properties. As a result, its incorporation in waterborne acrylic containing formulations as an equivalent to petrochemical-based methyl methacrylate was investigated. It was found that the bio-based monomer exhibited similar behavior to that of common methacrylates, as shown by polymerization kinetics and particle size evolution. Furthermore, the homogeneous incorporation of the sugar units into the acrylate chains was confirmed by a unique glass transition temperature in differential scanning calorimeter (DSC). The potential of MF for the production of waterborne copolymers was greatly valued by the successful increase of formulation solids content up to 45 wt %. Interestingly, polymer insolubility in tetrahydrofurane increased with time due to further reactions occurring in storage. Most likely, the partial deprotection of sugar units was the reason for the creation of hydrogen bonding and, thus, physically insoluble entangled chains. This behavior highlights opportunities to make use of hydroxyl groups either for further functionalization or, eventually, for achieving enhanced adhesion on casted substrates. Full article

(This article belongs to the Special Issue Emulsion Polymerization)

► Show Figures

Graphical abstract

14 pages, 2316 KiB

Open AccessArticle

One-Pot Synthesis of Waterborne Polymeric Dispersions Stabilized with Alkali-Soluble Resins

by Massimo Bandiera, Roelof Balk and Maria J. Barandiaran

Polymers 2018, 10(1), 88; https://doi.org/10.3390/polym10010088 - 18 Jan 2018

Cited by 15 | Viewed by 5364

Abstract

Alkali-soluble resins (ASRs) are a type of electrosteric emulsifiers of high interest because they can profitably improve the features of waterborne dispersions. In this work, they have been synthesized in-situ through a one-pot approach and they have been used as polymeric surfactants for [...] Read more.

Alkali-soluble resins (ASRs) are a type of electrosteric emulsifiers of high interest because they can profitably improve the features of waterborne dispersions. In this work, they have been synthesized in-situ through a one-pot approach and they have been used as polymeric surfactants for a second emulsion polymerization step in the same reactor. This strategy provides some advantages compared to other polymerization techniques, like the intensification of the process and the absence of organic solvents. Their use can also further reduce the environmental impact of formulations for film-forming applications, since grafting reactions with the particles have been observed and quantified in relation with the synthetic parameters. These chemical linkages with the particles may reduce the leaching and the release of surfactants from polymeric films, for example in water-based coatings or adhesives. The systems have been also studied from the kinetics point of view, finding relevant differences with other electrosterically stabilized processes from the literature, as well as concerns the nucleation mechanism. Full article

(This article belongs to the Special Issue Emulsion Polymerization)

► Show Figures

Graphical abstract

3450 KiB

Open AccessArticle

Surfactant-Free RAFT Emulsion Polymerization of Styrene Using Thermoresponsive macroRAFT Agents: Towards Smart Well-Defined Block Copolymers with High Molecular Weights

by Steffen Eggers and Volker Abetz

Polymers 2017, 9(12), 668; https://doi.org/10.3390/polym9120668 - 03 Dec 2017

Cited by 17 | Viewed by 8594

Abstract

The combination of reversible addition–fragmentation chain transfer (RAFT) and emulsion polymerization has recently attracted much attention as a synthetic tool for high-molecular-weight block copolymers and their micellar nano-objects. Up to recently, though, the use of thermoresponsive polymers as both macroRAFT agents and latex [...] Read more.

The combination of reversible addition–fragmentation chain transfer (RAFT) and emulsion polymerization has recently attracted much attention as a synthetic tool for high-molecular-weight block copolymers and their micellar nano-objects. Up to recently, though, the use of thermoresponsive polymers as both macroRAFT agents and latex stabilizers was impossible in aqueous media due to their hydrophobicity at the usually high polymerization temperatures. In this work, we present a straightforward surfactant-free RAFT emulsion polymerization to obtain thermoresponsive styrenic block copolymers with molecular weights of around 100 kDa and their well-defined latexes. The stability of the aqueous latexes is achieved by adding 20 vol % of the cosolvent 1,4-dioxane (DOX), increasing the phase transition temperature (PTT) of the used thermoresponsive poly(N-acryloylpyrrolidine) (PAPy) macroRAFT agents above the polymerization temperature. Furthermore, this cosolvent approach is combined with the use of poly(N,N-dimethylacrylamide)-block-poly(N-acryloylpiperidine-co-N-acryloylpyrrolidine) (PDMA-b-P(APi-co-APy)) as the macroRAFT agent owning a short stabilizing PDMA end block and a widely adjustable PTT of the P(APi-co-APy) block in between 4 and 47 °C. The temperature-induced collapse of the latter under emulsion polymerization conditions leads to the formation of RAFT nanoreactors, which allows for a very fast chain growth of the polystyrene (PS) block. In dynamic light scattering (DLS), as well as cryo-transmission electron microscopy (cryoTEM), moreover, all created latexes indeed reveal a high (temperature) stability and a reversible collapse of the thermoresponsive coronal block upon heating. Hence, this paper pioneers a versatile way towards amphiphilic thermoresponsive high-molecular-weight block copolymers and their nano-objects with tailored corona switchability. Full article

(This article belongs to the Special Issue Emulsion Polymerization)

► Show Figures

Graphical abstract

3307 KiB

Open AccessArticle

Controlled Release of Lysozyme from Double-Walled Poly(Lactide-Co-Glycolide) (PLGA) Microspheres

by Rezaul H. Ansary, Mokhlesur M. Rahman, Nasir Mohamad, Tengku M. Arrif, Ahmad Zubaidi A. Latif, Haliza Katas, Wan Sani B. Wan Nik and Mohamed B. Awang

Polymers 2017, 9(10), 485; https://doi.org/10.3390/polym9100485 - 03 Oct 2017

Cited by 14 | Viewed by 6417

Abstract

Double-walled microspheres based on poly(lactide-co-glycolide) (PLGA) are potential delivery systems for reducing a very high initial burst release of encapsulated protein and peptide drugs. In this study, double-walled microspheres made of glucose core, hydroxyl-terminated poly(lactide-co-glycolide) (Glu-PLGA), and carboxyl-terminated PLGA [...] Read more.

Double-walled microspheres based on poly(lactide-co-glycolide) (PLGA) are potential delivery systems for reducing a very high initial burst release of encapsulated protein and peptide drugs. In this study, double-walled microspheres made of glucose core, hydroxyl-terminated poly(lactide-co-glycolide) (Glu-PLGA), and carboxyl-terminated PLGA were fabricated using a modified water-in-oil-in-oil-in-water (w1/o/o/w2) emulsion solvent evaporation technique for the controlled release of a model protein, lysozyme. Microspheres size, morphology, encapsulation efficiency, lysozyme in vitro release profiles, bioactivity, and structural integrity, were evaluated. Scanning electron microscopy (SEM) images revealed that double-walled microspheres comprising of Glu-PLGA and PLGA with a mass ratio of 1:1 have a spherical shape and smooth surfaces. A statistically significant increase in the encapsulation efficiency (82.52% ± 3.28%) was achieved when 1% (w/v) polyvinyl alcohol (PVA) and 2.5% (w/v) trehalose were incorporated in the internal and external aqueous phase, respectively, during emulsification. Double-walled microspheres prepared together with excipients (PVA and trehalose) showed a better control release of lysozyme. The released lysozyme was fully bioactive, and its structural integrity was slightly affected during microspheres fabrication and in vitro release studies. Therefore, double-walled microspheres made of Glu-PLGA and PLGA together with excipients (PVA and trehalose) provide a controlled and sustained release for lysozyme. Full article

(This article belongs to the Special Issue Emulsion Polymerization)

► Show Figures

Figure 1

2753 KiB

Open AccessArticle

Combining Pickering Emulsion Polymerization with Molecular Imprinting to Prepare Polymer Microspheres for Selective Solid-Phase Extraction of Malachite Green

by Weixin Liang, Huawen Hu, Pengran Guo, Yanfang Ma, Peiying Li, Wenrou Zheng and Min Zhang

Polymers 2017, 9(8), 344; https://doi.org/10.3390/polym9080344 - 06 Aug 2017

Cited by 17 | Viewed by 6073

Abstract

Malachite green (MG) is currently posing a carcinogenic threat to the safety of human lives; therefore, it is highly desirable to develop an effective method for fast trace detection of MG. Herein, for the first time, this paper presents a systematic study on [...] Read more.

Malachite green (MG) is currently posing a carcinogenic threat to the safety of human lives; therefore, it is highly desirable to develop an effective method for fast trace detection of MG. Herein, for the first time, this paper presents a systematic study on polymer microspheres, being prepared by combined Pickering emulsion polymerization and molecular imprinting, to detect and purify MG. The microspheres, molecularly imprinted with MG, show enhanced adsorption selectivity to MG, despite a somewhat lowered adsorption capacity, as compared to the counterpart without molecular imprinting. Structural features and adsorption performance of these microspheres are elucidated by different characterizations and kinetic and thermodynamic analyses. The surface of the molecularly imprinted polymer microspheres (M-PMs) exhibits regular pores of uniform pore size distribution, endowing M-PMs with impressive adsorption selectivity to MG. In contrast, the microspheres without molecular imprinting show a larger average particle diameter and an uneven porous surface (with roughness and a large pore size), causing a lower adsorption selectivity to MG despite a higher adsorption capacity. Various adsorption conditions are investigated, such as pH and initial concentration of the solution with MG, for optimizing the adsorption performance of M-PMs in selectively tackling MG. The adsorption kinetics and thermodynamics are deeply discussed and analyzed, so as to provide a full picture of the adsorption behaviors of the polymer microspheres with and without the molecular imprinting. Significantly, M-PMs show promising solid-phase extraction column applications for recovering MG in a continuous extraction manner. Full article

(This article belongs to the Special Issue Emulsion Polymerization)

► Show Figures

Graphical abstract

2541 KiB

Open AccessArticle

Electronically Stabilized Copoly(Styrene-Acrylic Acid) Submicrocapsules Prepared by Miniemulsion Copolymerization

by Minkwan Kim, Yura Hwang and Han Do Ghim

Polymers 2017, 9(7), 291; https://doi.org/10.3390/polym9070291 - 20 Jul 2017

Cited by 5 | Viewed by 4580

Abstract

This work reports the preparation and characterization of poly(styrene-acrylic acid) (St/AA) submicrocapsules by using the miniemulsion copolymerization method. AA was introduced to miniemulsion polymerization of St to increase the zeta potential and the resulting electrostatic stability of St/AA submicrocapsules. Phytoncide oil was adopted [...] Read more.

This work reports the preparation and characterization of poly(styrene-acrylic acid) (St/AA) submicrocapsules by using the miniemulsion copolymerization method. AA was introduced to miniemulsion polymerization of St to increase the zeta potential and the resulting electrostatic stability of St/AA submicrocapsules. Phytoncide oil was adopted as the core model material. Miniemulsion copolymerization of St and AA was conducted at a fixed monomer concentration (0.172 mol) with a varying monomer feed ratio [AA]/[St] (0.2, 0.25, 0.33, 0.5, and 1.0). Concentrations of initiator (azobisisobutyronitrile; 1.0 × 10⁻³, 2.0 × 10⁻³, 3.0 × 10⁻³, and 4.0 × 10⁻³ mol/mol of monomer) and surfactant (sodium dodecyl sulfate; 0.6 × 10⁻³, 1.0 × 10⁻³, and 1.4 × 10⁻³ mol) were also controlled to optimize the miniemulsion copolymerization of St and AA. Dynamic light scattering and microscopic analyses confirmed the optimum condition of miniemulsion copolymerization of St and AA. Long-term colloidal stability of aqueous St/AA submicrocapsule suspension was evaluated by using Turbiscan^TM Lab. In this work, the optimum condition for miniemulsion copolymerization of St and AA was determined ([AA]/[St] = 0.33; [SDS] = 1.0 × 10⁻³ mol; [AIBN] = 2.0 × 10⁻³ mol/mol of monomer). St/AA submicrocapsules prepared at the optimum condition (392.6 nm and −55.2 mV of mean particle size and zeta potential, respectively) showed almost no variations in backscattering intensity (stable colloids without aggregation). Full article

(This article belongs to the Special Issue Emulsion Polymerization)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Emulsion Polymerization

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (8 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI