Mingwang Pan

Anisotropic Nanoparticles with Controllable Morphologies from Non‐Cross‐Linked Seeded Emulsion Polymerization

A simple and elegant approach to fabricate anisotropic P(VC-co-AAEM)/PS nanoparticles with controllable morphologies via emulsifier-free seeded emulsion polymerization is presented. Non-cross-linked P(VC-co-AAEM) seeds with hydrophilic surface are first synthesized through copolymerization of vinyl chloride (VC) and acetoacetoxyethyl methacrylate (AAEM), which are used to prepare P(VC-co-AAEM)/PS NPs with multiple bulges by SEP of styrene. Electron microscopy observation indicates that the content of AAEM in seeds is crucial to control the phase separation and morphology of the composite NPs. Moreover, the thermodynamic immiscibility between PVC and PS is the driving force for the formation of PS bulges onto the P(VC-co-AAEM) seeds. The resultant anisotropic NPs with non-cross-linked feature may promisingly serve as compatibilizers for further polymer processing.

Surface nucleation-induced fluoropolymer Janus nanoparticlesvia emulsifier-free batch-seeded emulsion polymerization

Nonspherical poly(vinylidene fluoride)/polystyrene (PVDF/PS) composite latex particles were prepared via a facile emulsifier-free batch-seeded emulsion polymerization. It was found that the styrene (St)/PVDF feed ratio was a determining factor for the formation of well-defined Janus particles. Transmission electron microscopy study revealed that the immiscibility between PVDF and St-swollen PS (PS/St) was the driving force for the dewetting and nucleation of PS/St bulges on the PVDF particle surface. When the St/PVDF feed ratio was high, easy fusion of multiple PS/St bulges into one single bulge on the PVDF particle resulted in well-defined PVDF/PS Janus particles. When the St/PVDF feed ratio was low, it was difficult for multiple bulges to fuse together to form PVDF/PS Janus particles.

Popcorn-like morphology of asymmetric nanoparticles co-adjusted by hydrophilicity and crosslinking degree of the seeds

This paper presents a facile synthesis method for poly(methyl methacrylate-co-acetoacetoxyethyl methacrylate)–polystyrene popcorn-like particles by soap-free seeded emulsion polymerization. In this study, popcorn-like, raspberry-like and reverse core–shell structures of the P(MMA-co-AAEM)–PS particles could be obtained in a reliable manner. And it was found that the hydrophilicity and crosslinking degree of the seed particles, which were respectively controlled by the addition amount of comonomer AAEM and crosslinker ethyleneglycol dimethacrylate in the P(MMA-co-AAEM) seed particles, co-adjusted the popcorn-like morphology of P(MMA-co-AAEM)–PS particles. In order to make sense of the formation mechanism of the morphology, a thermodynamic model utilizing an equilibrium among the elastic-retractile force of the cross-linked polymer network, the mixing force of monomer and polymer and the interfacial tension force between the particle and water, was used to explain the formation of anisotropic particles.

Intriguing Morphology Evolution from Noncrosslinked Poly(tert-butyl acrylate) Seeds with Polar Functional Groups in Soap-Free Emulsion Polymerization of Styrene.

Herein, we demonstrate a facile approach to prepare anisotropic poly(tert-butyl acrylate)/polystyrene (PtBA/PS) composite particles with controllable morphologies by soap-free seeded emulsion polymerization (SSEP). In the first step, noncrosslinked PtBA seeds with self-stabilizing polar functional groups (e.g., ester groups and radicals) are synthesized by soap-free emulsion polymerization. During the subsequent SSEP of styrene (St), PS bulges are nucleated on the PtBA seeds due to the microphase separation confined in the latex particles. The morphology evolution of PtBA/PS composite particles is tailored by varying the monomer/seed feed ratio, polymerization time, and polymerization temperature. Many intriguing morphologies, including hamburger-like, litchi-like, mushroom-like, strawberry-like, bowl-like, and snowman-like, have been acquired for PtBA/PS composite particles. The polar groups on the PtBA seed surface greatly influence the formation and further merging of PS/St bulges during the polymerization. A possible formation mechanism is proposed on the basis of experimental results. These complex composite particles are promising for applications in superhydrophobic coatings.

Nonspherical Nanoparticles with Controlled Morphologies via Seeded Surface-Initiated Single Electron Transfer Radical Polymerization in Soap-Free Emulsion

This work reports a facile novel approach to prepare asymmetric poly(vinylidene fluoride)/polystyrene (PVDF/PS) composite latex particles with controllable morphologies using one-step soap-free seeded emulsion polymerization, i.e., surface-initiated single electron transfer radical polymerization (SET-RP) of styrene (St) at the surface of PVDF seed particles. It was observed that the morphology was influenced mainly by the St/PVDF feed ratio, the polymerization temperature, and the length of the catalyst Cu(0) wire (Φ 1.00 mm). When the feed ratio was St/PVDF = 5.0 g/1.0 g, snowman-like Janus particles were exclusively obtained. Raspberry-like and popcorn-like composite particles were observed at a higher reaction temperature or a shorter length of the catalyst wire. The reaction kinetics plots demonstrated some unique features. The formation of nonspherical composite nanoparticles can be ascribed to the surface nucleation of PS bulges following the SET-RP.

Self-Assembled Colloidal Particle Clusters from In Situ Pickering-Like Emulsion Polymerization via Single Electron Transfer Mechanism.

A simple route is reported to synthesize colloidal particle clusters (CPCs) from self-assembly of in situ poly(vinylidene fluoride)/poly(styrene-co-tert-butyl acrylate) [PVDF/P(St-co-tBA)] Janus particles through one-pot seeded emulsion single electron transfer radical polymerization. In the in situ Pickering-like emulsion polymerization, the tBA/St/PVDF feed ratio and polymerization temperature are important for the formation of well-defined CPCs. When the tBA/St/PVDF feed ratio is 0.75 g/2.5 g/0.5 g and the reaction temperature is 35 °C, relatively uniform raspberry-like CPCs are obtained. The hydrophobicity of the P(St-co-tBA) domains and the affinity of PVDF to the aqueous environment are considered to be the driving force for the self-assembly of the in situ formed PVDF/P(St-co-tBA) Janus particles. The resultant raspberry-like CPCs with PVDF particles protruding outward may be promising for superhydrophobic smart coatings.

Morphology and film performance of phthalate-free plasticized poly(vinyl chloride) composite particles via the graft copolymerization of acrylate swelling flower-like latex particles

This study reports an intriguing preparation of a nontoxic and phthalate-free polyacrylate/poly(vinyl chloride)-swollen then grafted-polyacrylate (PBA/PVC-sg-PBA) for the production of flexible PVC by means of a multistage emulsion polymerization. Flower-like PBA/PVC composite particles with rich hydrophilic groups and functional end groups were first synthesized through the seeded emulsion polymerization of poly(butyl acrylate) (PBA), vinyl chloride (VC), 3-(trimethoxysilyl) propyl methacrylate (MPS), and allyl methacrylate (AMA), and then the anisotropic PBA/PVC composite particles were used as seeds to prepare PBA/PVC-sg-PBA composite particles. PBA is biologically safe without producing an acute toxicity response. This formation process was studied in detail, and the effects of the BA/(PBA/PVC) feed weight ratio on the PBA/PVC-sg-PBA composite particle morphology and mechanical properties of the prepared film materials were investigated. Scanning electron microscopy (SEM) observations indicated that the content of MPS in the PBA/PVC seeds was crucial to control the morphologies of the flower-like PBA/PVC composite particles. Transmission electron microscopy (TEM) illustrated that the PBA was uniformly dispersed in the PBA/PVC particles to form an interpenetrating network layer. Dynamic mechanical analysis (DMA) revealed that the compatibility between PBA and PVC was well improved with increasing PBA content. The flexibility of phthalate-free PBA/PVC-sg-PBA was comparable to the corresponding performance of a commercial PVC/DOP mixture, and its stretchability was superior to the PVC/DOP system.

Raspberry-like morphology of polyvinyl chloride/zinc oxide nanoparticles induced by surface interaction and formation of nanoporous foam

This work presents a facile approach to synthesize P(VC-co-AAEM) (vinyl chloride copolymerized acetoacetoxyethyl methacrylate)/zinc oxide (ZnO) nanocomposite particles with raspberry-like shape by a nano-coating technique. It is proved that the interactions between the β-diketone groups embedded in AAEM and ZnO precursors are crucial to forming the raspberry-like morphology, as such, the content of AAEM has a significant effect on the nucleation and growth of ZnO nanocrystals on the P(VC-co-AAEM) beads. SEM analysis demonstrated that ZnO nanocrystals were deposited on the surface of template nanoparticles as small clusters with different sizes and quantity, depending on the reaction parameters. X-ray diffraction of the P(VC-co-AAEM)/ZnO nanocomposite particles revealed that the addition of functionalized PVC beads lowered the formation of ZnO nanocrystals due to the constraining effect of the ZnO–AAEM interaction on the mobility of ZnO precursors. Additionally, such PVC/ZnO composite particles were found to have excellent foamability of nanometer-sized pores, which could have various potential applications in sound insulation and thermal insulation.

How Chain Intermixing Dictates the Polymorphism of PVDF in Poly(vinylidene fluoride)/Polymethylmethacrylate Binary System during Recrystallization: A Comparative Study on Core–Shell Particles and Latex Blend

In the past few decades, Poly(vinylidene fluoride)/Polymethylmethacrylate (PVDF/PMMA) binary blend has attracted substantial attention in the scientific community due to possible intriguing mechanical, optical and ferroelectric properties that are closely related to its multiple crystal structures/phases. However, the effect of PMMA phase on the polymorphism of PVDF, especially the relationship between miscibility and polymorphism, remains an open question and is not yet fully understood. In this work, three series of particle blends with varied levels of miscibility between PVDF and PMMA were prepared via seeded emulsion polymerization: PVDF–PMMA core–shell particle (PVDF@PMMA) with high miscibility; PVDF/PMMA latex blend with modest miscibility; and PVDF@c–PMMA (crosslinked PMMA) core–shell particle with negligible miscibility. The difference in miscibility, and the corresponding morphology and polymorphism were systematically studied to correlate the PMMA/PVDF miscibility with PVDF polymorphism. It is of interest to observe that the formation of polar β/γ phase during melt crystallization could be governed in two ways: dipole–dipole interaction and fast crystallization. For PVDF@PMMA and PVDF/PMMA systems, in which fast crystallization was unlikely triggered, higher content of β/γ phase, and intense suppression of crystallization temperature and capacity were observed in PVDF@PMMA, because high miscibility favored a higher intensity of overall dipole–dipole interaction and a longer interaction time. For PVDF@c–PMMA system, after a complete coverage of PVDF seeds by PMMA shells, nearly pure β/γ phase was obtained owing to the fast homogeneous nucleation. This is the first report that high miscibility between PVDF and PMMA could favor the formation of β/γ phase.