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应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE Coreshell polymers: a review RSC Adv. , 2013, 3, 15543-15565 Reporter: Rui Niu Jianwu Guo Xiaobo Teng 2013.11.20 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE Content 1.Introduction 2.Classifications 3.Preparation of core-shell 4.Development of latex particle morphology of CPS 5.Characterizations 6.Recent study on core-shell polymers 7.Applications 8.conclusion 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 1.Introduction In1961,Hughes and Brown investigated the physical properties of coreshell polymer (CSP) and their interesting morphology. This class of material has attracted much attention because of the combination of superior properties not possessed by the individual components. The systems might combine the characteristics and properties of both shell and core where the surface properties of the shell are translated to the core,imparting new functionality to the CSP. Macromolecules, 2003, 36 (6), 19881993. CSPs are structured composite particles consisting of at least two different components, one in principle forms the core and another forms the shell of the particles. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 2. Classification Core shell polymers (CSPs) State Hydrogels NIPAM Non-NIPAM Conventional monomer Acrylamide derivatives Size Nano Micro Non-Hydrogels Non-aqueous Organic-inorganic Single 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 2.1 Coreshell polymer hydrogels a hydrogel shell surrounding a non-hydrogel core Hydrogel in both core and shell components Coreshell polymer hydrogels Property: CSP hydrogels have been produced either to modify the stability and physical properties of the polymers or to impart stimuli- responsive properties to responsive particles. Application: CSP hydrogels made of smart materials have widespread applications, especially in biomedical areas, as their response to surrounding environmental changes such as temperature and pH,etc. Adv. Drug Delivery Rev. , 1996 ,18 (2), 219267. Macromolecules, 1998 ,31 (25), 89128917. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 2.1.1 NIPAM based CSP hydrogels 32 switchable or smart materials, poly (N - isopropylacrylamide PNIPAM) has been extensively used as a main component in CSP hydrogels due to its thermoresponsive properties. Macromolecules, 1998 , 31 (25), 89128917 Langmuir, 2004 ,20 (11), 43304335 J. Colloid Interface Sci. , 2012, 376 (1), 97106. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 2.1.2 Non-NIPAM CSP hydrogel non-NIPAM CSPs (conventional monomer ) hydrophilic AAm hydrophilic AAc hydrophobic MMA hydrophobic St. produce responsive CSPs non-NIPAM CSPs (acrylamide derivatives) NIPMAM NNPAM N-ethylacrylamide N-vinylisobutylacrylamide used to polymerize temperature-sensitive microgels 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 2.2 Non-hydrogel coreshell polymer Non Hydrogels Non-aqueous Organic-inorganic Single Core: solid polymer particle or rubber Shell: hard polymer Used: paints, coating applications, pigments, binder Used：nanotechnology and biomedical applications, such as a signal-molecular template , live-cell imaging, drug carrier and drug release. Def: non-cross linked CSPs consisting of amphiphilic block or graft polymers in which hydrophobic and hydrophilic segments are covalently connected with the dendritic or hyperbranched core-shell. 在下面介绍 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE J. Am. Chem. Soc. , 2010 , 132(35), 1221812221 synthesis of new functional materials for light-emitting devices, solar cells, photodetectors , biomedical and sensor applications. Core surfactant poly (ethylene oxide) poly (vinyl benzyl chloride) poly (vinyl pyrrolidone ) polymer different copolymers poly ( styrene acrylic acid) Shell metals metal oxides metal chalcogenides silica Adv. Mater. , 2009 ,21 (5), 509534. J. Mater. Chem. , 2012 ,22 (22), 1137011378. Used Inorganicorganic CSPs butadiene styrene 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 3. Preparation of coreshell polymers CSPs are typically prepared by a series of consecutive, emulsion, dispersion or precipitation polymerization sequences with different monomer type. CSP particles lmulti-step l One-stage reaction: a facile method to prepare polymer particles with coreshell morphology. seed particles as a core material second or third stage monomer is polymerized in the seed latex particles Disadvantage: expensive , timeconsuming Chim. Acta, 2003 , 496(12), 5363. Macromolecules, 2009 ,42 (13), 45114519. consecutive emulsion 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE lDispersion polymerization： a class of larger particles and irregular shape of polymer particles were produced in precipitation polymerization. polymer particles in the range of 115 m. The formed polymers are insoluble in continuous phase . Based on ploymerization classes lemulsion polymerization : the main process for the preparation of commercial emulsion, which involves a monomer that has limited solubility in water. particle diameter is typically within the range of 110 m. Macromolecules, 2009 ,42 (13), 45114519 Part A: Polym. Chem. , 2001 ,39 (19), 34343442 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE Example Fig. 3 illustrates common methods to prepare CSPs described by Li and Stover. emulsion polymerization using reactive surfactants Two-stage emulsion polymerization was the first general method step-wise heterocoagulation of smaller cationic polymer particles onto larger anionic, heat treatment . block copolymers can be used to produce coreshell type polymer nanospheres via block copolymerization . 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 3.1 Emulsion polymerization Emulsion polymerization synthesized process is commonly used to produce water based resins with a variety of physicochemical and colloidal properties. Characterized :emulsified monomer droplets (1-10 um in diameter) dispersed in a continuous aqueous phase with the assistance of an oil-in-water surfactant at the very beginning of polymerization. The emulsion polymerization technique is a commercially and technologically important reaction system. This technique continues to grow through its versatile reaction and its ability to tailor the properties of the emulsion polymer produced. Emulsion polymerization semi-batch process batch process 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE The most significant difference between batch and semi-batch emulsion polymerization l Semi-batch process allows two types of feed stream, M ( monomer) feed and E (emulsion) feeds l Batch processes are of limited versatility for producing emulsion and are mainly use in academic research with simple reaction formulations. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE Advantage of Semi-bath: (1) Good temperature control with extra cooling of polymerization process. (2) Easy to control polymerization rate by keeping process starved. (3) Flexible control of molecular weight. (4) Good polymer composition control. uExample one Lin et al. prepared thermoresponsive CSPs of P(NIPAM-co-AAc) or poly (NIPAM-co-SA) copolymer using batch process surfactant-free emulsion copolymerization (SFEP). CSPs Reactant 2h 70 200rpm Milky white and average diameter of 200 to 500 nm NIPAM-co-AAc PH3-4 NIPAM-co-SA PH6-6.2 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE uExample two Fig. 6 A schematic representation of the copolymerization and cross-linking reaction mechanism of AN with NIPAM in sodium dodecyl sulfate (SDS) micelles. Serrano-Medina prepared nano/microgels of poly (P(NIPAM-co-PEGMEMA-co- 2MBA) by one-stage surfactant free emulsion polymerization (SFEP) The high sensitivity of these P(NIPAM-co-AAc) microgels to small changes in pH and temperature suggest that they could be useful in drug delivery applications 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE uExample three Fig. 7 Schematic representation of the formation of the coreshell NPs by semi- batch emulsion polymerization. Reproduced from ref. 83 by permission of American Chemical Society. Ni et al. synthesized hybrid nanoparticles (NPs) with a polystyrene core and a hybrid copolymer shell in a two step process: emulsion polymerization of styrene and subsequent copolymerization of styrene with -methacryloxypropyltri- methoxysilane (MPS). 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 3.2 Dispersion polymerization This technique allows synthesis of micro particles in the range of 115microns. Most of the ingredients in this process, including surfactant, initiators and monomers, are soluble in continuous organic phase and which form polymers that are insoluble in continuous phase. uExample Li et al. reported the preparation of narrowly distributed nanogels by two-stages dispersion polymerization. First, the core particles composed of PNIPAM were synthesized and then the core particles were used as nuclei in the following stage for subsequent shell addition of poly(4-vinylpyridine) (P4VP)(四乙烯基吡 啶). 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 3.3 Other techniques to prepare coreshell polymers uExample one three-step synthesis approach was used to prepare thermoresponsive CSP by Xiao et al. A single-molecular particle of hyperbranched conjugated polyelectrolyte (HCPE) was synthesized by Pu et al. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE uExample two Fig. 9 shows a schematic illustration of the synthesis routes of single-molecular nano-particles multi-HPBPEA-g- PNIPAM Three-step synthesis approach was used to prepare thermoresponsive CSP by Cai and Liu to synthesize a novel single-molecular/unimolecular nanoparticle, multi hyperbranched poly2-(2-bromopropionyl)oxy) ethyl acrylate)-g-poly ( Nisopropylacrylamide (HPBPEA-g-PNIPAM), via atom transfer radical polymerization (ATRP). 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE Mu et al. prepared a monodisperse and multilayer coreshell (MMLCS) via surface cross-linking emulsion polymerization. uExample three Fig. 10 shows the preparation of multilayer coreshell (MMLCS) emulsion via surface cross -linking emulsion polymerization. The PBA core was synthesized by seed polymerization using the PBA seed at 75 2 for 3.5 h. GMA:甲基丙烯酸缩水甘油酯 BA：丁基丙烯酸酯 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE uExample four Thermosensitive PStPNIPAM coreshell particles were synthesized using photoemulsion polymerization technique. This new synthesis strategy may Produce a thermosensitive shell of PNIPAM networks with more homogeneous cross-linking density. uExample five 5 mol% NIPAM Kim et al. fabricated monodisperse coreshell microgels based PNIPAM by capillary microfluidic technique. Used to develop novel biomaterials for applications in drug delivery, artificial muscles, and cancer therapy. Fig. 12 Drop formation of pre-microgel drops in a capillary microfluidic device. （毛细管装 置中微凝胶的液滴状微流动图示意图） 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 4. Development of latex particle morphology of CSP Affected by many variables cross-linking radical penetration diffusion processing polarity of monomers batch processingsemi-batch processing 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 4.1 Effect of cross-linking Durant et al. have predicted the effect of cross-linked seed latex particles on equilibrium particle morphology of two component particles, which is considered to be occluded morphology (OCC), inverse coreshell (ICS) and coreshell (CS) structures. Sheu et al. prepared core-shell latices by seeded emulsion polymerization of styrene (St) into polystyrene (PSt) latices with varying amounts of DVB cross-linker. uExample one uExample two Fig. 14. PSt formed a homogeneous shell on uncross-linked PSt seed. The morphology of the shell changed to a snowman structure when PSt seed was cross-linked with around 0.2% of DVB. At 6% of DVB the shape of the shell changed into a raspberry structure. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 4.2 Radical penetration and diffusion Fig. 15 Possible particle morphologies produced from differing radical penetration depth. Reproduced from ref. 100 and 104 by permission of Elsevier and Taylor & Francis. monomers Latex particle penetrates Ivarsson et al. and Jo nsson studied the influence of the relative difference apparent between glass transition temperature, Tg, and reaction temperature within particle on the ability of oligomeric radicals. One hand On the other hand polymer radicals may be restricted to the periphery of the particles when the radical flux is high enough and the monomer feed is slow enough for glassy seed polymers, but probably not for low Tg seed polymers. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 5. Characterizations TEM and SEM 1H and13C nuclear magnetic resonance spectroscopy (NMR) Small angle neutron scattering (SANS) Nonradioactive direct energy transfer (NRET) Photon correlation spectroscopy (PCS) Dynamic light scattering (DLS) 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE 6. Recent study on coreshell polymers Coreshell polymers have attracted enormous research interest, both from the point of view of fundamental science and for prospective applications. In addition, the unique properties of CSP attracted scientists to study and developed new microgel systems and re- investigated older systems using advanced techniques and methods. Example one Yu et al. prepared monodisperse CS microspheres composed of a PNIPAM-co-PHEMA by microfluidic emulsification, freeradical polymerization and ATRP. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE Example two Lee et al. demonstrated that coreshell poly (styrene/ pyrrole) P(St/Py) particles were successfully prepared by using Fe3+-catalyzed oxidative polymerization with emulsifier-free emulsion polymerization in aqueous medium. The resulting P(St/Py) particles showed excellent electrical conductivity (2.21 Scm-1) due to the coreshell morphology. Fig. 26(a) shows a schematic for the formation of coreshell P(St/Py) particles and (b) the detailed reaction mechanism of pyrrole monomers via Fe3+-catalyzed oxidative polymerization. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE Example three Zhang et al. reported a facile method to create a living in situ gelling system for controlled formation of hydrogels from a hyperbranched polymer (BAP) with disulfide-linked coreshell structures. Contribution: they developed an inverse emulsion technique to obtain micro or nanodroplets of a disulfide-linked core shell BAP. To produce fine-tunable micro/nano drug carriers, having broad implications in diagnostics and therapeutic delivery systems Fig. 27 (A) Schematic illustration of the core/shell separation process dissociation of the shells and cross-linking of the cores and (B) schematic depiction of the synthetic approach to controlled formation of (multilayered) hydrogel particles. 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE Example four a, Schematic illustration of a core-shell microgel which undergoes three regions of different swelling behavior (completely reversible process). b, corresponding classification of previously mentioned regions in an exemplary Rh(T)-diagram of a core-shell microgel system with 10 mol% cross-linked cores. In region I we find a restricted shell collapse, while region II covers the linear swelling behavior. Region III indicates the occurrence of an active core collapse. Zeiser et al. PNIPMAM- co-PNNPAM .In the region between 25 and 41 , the response of the particles is directly proportional to the temperature。 应用表面与胶体化学教育部重点实验室 Key Laboratory of Applied Chemistry & C