Synthesis, Characterization, and Pickering Emulsifier Performance of Anisotropic Cross-Linked Block Copolymer Worms: Effect of Aspect Ratio on Emulsion Stability in the Presence of Surfactant
Saul J. HunterKate L. ThompsonJoseph R. LovettFiona L. HattonMatthew J. DerryChristopher LindsayPhilip TaylorSteven P. Armes
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Abstract:
Reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization is used to prepare epoxy-functional PGMA-P(HPMA- stat-GlyMA) diblock copolymer worms, where GMA, HPMA, and GlyMA denote glycerol monomethacrylate, 2-hydroxypropyl methacrylate, and glycidyl methacrylate, respectively. The epoxy groups on the GlyMA residues were ring-opened using 3-aminopropyltriethoxysilane (APTES) in order to cross-link the worm cores via a series of hydrolysis-condensation reactions. Importantly, the worm aspect ratio can be adjusted depending on the precise conditions selected for covalent stabilization. Relatively long cross-linked worms are obtained by reaction with APTES at 20 °C, whereas much shorter worms with essentially the same copolymer composition are formed by cooling the linear worms from 20 to 4 °C prior to APTES addition. Small-angle X-ray scattering (SAXS) studies confirmed that the mean aspect ratio for the long worms is approximately eight times greater than that for the short worms. Aqueous electrophoresis studies indicated that both types of cross-linked worms acquired weak cationic surface charge at low pH as a result of protonation of APTES-derived secondary amine groups within the nanoparticle cores. These cross-linked worms were evaluated as emulsifiers for the stabilization of n-dodecane-in-water emulsions via high-shear homogenization at 20 °C and pH 8. Increasing the copolymer concentration led to a reduction in mean droplet diameter, indicating that APTES cross-linking was sufficient to allow the nanoparticles to adsorb intact at the oil/water interface and hence produce genuine Pickering emulsions, rather than undergo in situ dissociation to form surface-active diblock copolymer chains. In surfactant challenge studies, the relatively long worms required a thirty-fold higher concentration of a nonionic surfactant (Tween 80) to be displaced from the n-dodecane-water interface compared to the short worms. This suggests that the former nanoparticles are much more strongly adsorbed than the latter, indicating that significantly greater Pickering emulsion stability can be achieved by using highly anisotropic worms. In contrast, colloidosomes prepared by reacting the hydroxyl-functional adsorbed worms with an oil-soluble polymeric diisocyanate remained intact when exposed to high concentrations of Tween 80.Keywords:
Glycidyl methacrylate
Cationic polymerization
Pickering emulsion
水に浸潰したときの3種の組成(メタグリル酸エチル(EMA)/メタクリル酸グリシジル(GMA)=9/1,8/2,713モル比)の共重合体の収着過程をζポテンシャルの経時的減少過程から追究した。共重合体のガラス転移点Tgを含む温度範囲(室温から約80℃)で測定した。ζポテンシャル(流動電位法から求まる)から得られる速度定数Kを収着から直接得られる拡散定数Dと比較した。その結果は以下のとおりである。(1)Kは収着過程の組成依存を明確に示した。すなわち, GMAの増加にしたがってT > Tgにおける活性化エネルギー E 1 2(負)は増加し, T > T,における活性化エネルギー E l zは減少した。(2)Dから得られる活性化エネルギー(E 1 S と E 2 s)は組成依存を明確には示さなかった。しかし,室温に近い温度においては収着量への水和の寄与がみられた(組成8/2と7/3共重合体)。
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Abstract To synthesize a matrix for the immobilization of enzymes, alginic acid, a naturally occurring polysaccharide has been chosen as the backbone, and glycidyl methacrylate (GMA) and 2‐hydroxy ethyl methacrylate (HEMA) as monomers for graft copolymerization. HEMA was used to introduce hydrophilic character which would have been lost during the introduction of the hydrophobic monomer glycidyl methacrylate into alginic acid. Immobilization of trypsin onto this matrix takes place by covalent bonding. The temperature optimum of the immobilized enzyme was found to be 35°C and it was most stable at pH 8.
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This study proposes to use reactive copolymers based on glycidyl methacrylate and fluoroalkyl methacrylates with a low fluorine content in the monomer unit as agents to reduce the surface free energy (SFE). This work reveals the effect of the structure and composition of copolymers on the SFE and water-repellent properties of these coatings. On a smooth surface, coatings based on copolymers of glycidyl methacrylate and fluoroalkyl methacrylates with fluorine atoms in the monomer unit ranging from three to seven are characterized by SFE values in the range from 25 to 13 mN/m, which is comparable to the values for polyhedral oligomeric silsesquioxanes and perfluoroalkyl acrylates. On textured aluminum surfaces, the obtained coatings provide time-stable superhydrophobic properties with contact angles up to 170° and sliding angles up to 2°. The possibility of using copolymers based on glycidyl methacrylate and fluoroalkyl methacrylates for the creation of self-cleaning polymer coatings is shown.
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Abstract Poly(glycidyl methacrylate‐ co ‐ethyl methacrylate) and poly(glycidyl methacrylate‐ co ‐butyl methacrylate) random copolymers (with 50–50 mol % of monomers) were made radiopaque by grafting iodine moieties through the ring opening reaction of the epoxy groups. The percentage weight of grafted iodine in the copolymers was found to be as high as 19%. The iodinated copolymers showed higher glass transition temperature and thermal stability in comparison with the parent copolymers. Iodinated copolymer of poly(glycidyl methacrylate‐ co ‐ethyl methacrylate) has improved glass transistion temperature than iodinated poly(glycidyl methacrylate‐ co ‐butyl methacrylate). Radiographic analysis of these iodinated copolymers showed excellent radiopacity. The in vitro cytotoxicity tests revealed cytocompatibility with cells. These radiopaque copolymers are expected to find application as dental and orthopedic cements. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
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Glycidyl methacrylate
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Abstract A series of macroporous membrances composed either of glycidyl methacrylate and ethylene dimethacrylate with an addition of other monomer chosen from a group comprising 2‐hydroxyethyl methacrylate, butyl methacrylate, octyl methacrylate or dodecyl methacrylate, or of a copolymer of 2‐hydroxyethyl methacrylate and ethylene dimethacrylate were synthesized and their properties were determined. The addition of a third monomer changes the porous properties only when the concentration of the monomer in the polymerization feed is rather high. The presence of bulkier alkyl side chains in a polymer matrix raises hydrophobicity and reduces the water regain while the strength of the membrane increases.
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Ethylene glycol dimethacrylate
2-Hydroxyethyl Methacrylate
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メタクリル酸ジエチルアミノェチル(DEA)およびメタクリル酸グリシジル(GMA)とスチレン(St)の溶液共低重合を80℃,開始剤濃度おのおの[AIBN]=5×10-3,1×10-2(mol/l)で行なった。単量体反応性比はDEA-St共低重合体では溶媒種によって影響を受けるが,GMA-St共低重合体では塊状重合の場合とほとんど同じ値を示す。重合速度と仕込み共重合体組成の関係はSt組成が多いところほど重合速度は小さくなる傾向にある。DEA-St共重合における交媒停止定数はφ=5であり,小さい値であるので,この系では交媒停止が生起し難い。重合速度と開始剤濃度および単量体濃度の関係はRp∝[AIBN]0.5[M]の関係があり,したがって,この系では2分子停止が生起する。DEA-St共低重合反応,80℃におけるみかけの連鎖移動定数はCs'=1.33×10-3(トルエン),Cs'=2.36×10-3(四塩化炭素)であり,これをStの80℃におけるラジカル重合と比較すると,四塩化炭素のCs′は小さく,トルエンでは大きい値となる。DEA-St共低重合体の融点は共低重合体組成比によって著しく影響され,スチレン組成に富む共低重合体ほど融点は高くなる傾向を示す。共重合体のDEA中のジエチルアミノ基とヨウ化メチルの第四級アンモニウム化反応を行なった。反応はほぼ100%起こり,反応生成物はジメチルホルムアミド以外のほとんどの有機溶媒に不溶であるが,水には良く溶け,反応前の共重合体がほとんどの有機溶媒に良く溶け,水には不溶であったのとは対称的である。
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Glycidyl methacrylate
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