应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOECoreshell polymers: a reviewRSCAdv.,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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEContent1.Introduction2.Classifications3.Preparation of core-shell4.Development of latex particle morphology of CPS5.Characterizations 6.Recent study on core-shell polymers7.Applications8.conclusion应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE1.IntroductionIn1961,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 leasttwo 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE2. Classification Core shell polymers(CSPs)StateHydrogelsNIPAM Non-NIPAMConventionalmonomerAcrylamide derivativesSizeNanoMicroNon-HydrogelsNon-aqueousOrganic-inorganicSingle应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE2.1 Coreshell polymer hydrogelsa hydrogel shell surrounding a non-hydrogel coreHydrogel in both core and shell componentsCoreshell polymer hydrogelsProperty: 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.DrugDeliveryRev.,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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE2.1.1 NIPAM based CSP hydrogels32switchable 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),89128917Langmuir,2004,20(11),43304335 J.ColloidInterfaceSci.,2012,376(1),97106.应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE2.1.2 Non-NIPAM CSP hydrogelnon-NIPAM CSPs (conventional monomer )hydrophilic AAmhydrophilic AAchydrophobic MMAhydrophobic St.produce responsive CSPsnon-NIPAM CSPs (acrylamide derivatives)NIPMAMNNPAMN-ethylacrylamideN-vinylisobutylacrylamideused to polymerize temperature-sensitive microgels应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE2.2 Non-hydrogel coreshell polymerNon HydrogelsNon-aqueousOrganic-inorganicSingleCore: solid polymer particle or rubberShell: hard polymerUsed: paints, coating applications, pigments, binderUsed： ：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.在下面介绍在下面介绍应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEJ.Am.Chem.Soc.,2010,132(35),1221812221synthesis of new functional materials for light-emitting devices, solar cells, photodetectors , biomedical and sensor applications. Coresurfactantpoly (ethylene oxide)poly (vinyl benzyl chloride)poly (vinyl pyrrolidone )polymerdifferent copolymerspoly ( styrene acrylic acid)Shellmetalsmetal oxidesmetal chalcogenides silicaAdv.Mater.,2009,21(5),509534.J.Mater.Chem.,2012,22(22),1137011378.UsedInorganicorganic CSPsbutadienestyrene应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE3. Preparation of coreshell polymersCSPs are typically prepared by a series of consecutive, emulsion, dispersion or precipitation polymerization sequences with different monomer type.CSP particleslmulti-stepl 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 particlesDisadvantage: expensive , timeconsumingChim.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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOElDispersion 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 classeslemulsion 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),45114519PartA:Polym.Chem.,2001,39(19),34343442应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEExample 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 methodstep-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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE3.1 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 polymerizationsemi-batch processbatch process应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEThe most significant difference between batch and semi-batch emulsion polymerizationl Semi-batch process allows two types of feed stream, M ( monomer) feed and E (emulsion) feedsl 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 Linetal. prepared thermoresponsive CSPs of P(NIPAM-co-AAc) or poly (NIPAM-co-SA) copolymer using batch process surfactant-free emulsion copolymerization (SFEP). CSPs Reactant2h70200rpmMilky white and average diameter of 200 to 500 nmNIPAM-co-AAcPH3-4NIPAM-co-SAPH6-6.2应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEuExample twoFig. 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEuExample threeFig. 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE3.2 Dispersion polymerizationThis 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE3.3 Other techniques to prepare coreshell polymersuExample onethree-step synthesis approach was used to prepare thermoresponsive CSP by Xiao et al.A single-molecular particle of hyperbranched conjugatedpolyelectrolyte (HCPE) was synthesized by Puetal.应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEuExample two Fig. 9 shows a schematic illustration of the synthesis routes of single-molecular nano-particles multi-HPBPEA-g-PNIPAMThree-step synthesis approach was used to prepare thermoresponsive CSP by Cai and Liu to synthesize a novel single-molecular/unimolecularnanoparticle, multihyperbranchedpoly2-(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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEMuetal. prepared a monodisperse and multilayer coreshell (MMLCS) via surface cross-linking emulsion polymerization.uExample threeFig. 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 2for 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEuExample fourThermosensitive PStPNIPAM coreshell particles were synthesized using photoemulsion polymerization technique. This new synthesis strategy may Produce a thermosensitive shell of PNIPAM networks with morehomogeneous cross-linking density.uExample five5 mol% NIPAMKim et al. fabricated monodisperse coreshell microgels based PNIPAM by capillary microfluidic technique.Used to develop novel biomaterials forapplications in drug delivery, artificialmuscles, 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE4. Development of latex particle morphology of CSPAffected by many variablescross-linkingradical penetration diffusionprocessing polarity of monomersbatch processingsemi-batch processing应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE4.1 Effect of cross-linkingDurant 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.Sheuetal. prepared core-shelllatices by seeded emulsionpolymerization of styrene (St) into polystyrene (PSt) laticeswith varying amounts of DVB cross-linker.uExample oneuExample twoFig. 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE4.2 Radical penetration and diffusionFig. 15 Possible particle morphologies produced from differing radical penetration depth. Reproduced from ref. 100 and 104 by permission of Elsevier and Taylor & Francis.monomersLatex particlepenetratesIvarsson 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 handpolymer 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE5. CharacterizationsTEM 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE6. Recent study on coreshell polymersCoreshell 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 oneYu et al. prepared monodisperse CSmicrospheres 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEExample twoLee 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEExample threeZhang 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 coreshell BAP. To produce fine-tunable micro/nano drug carriers, having broad implications in diagnostics and therapeutic delivery systemsFig. 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEExample 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应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOEExample fivePeng et al. studied a novel approach for preparing hollow PSt particles by seed emulsion polymerization. The particles are composed of PNIPAM-co-PSt and Hollow particles have shown potential applications in drug delivery , catalysts, controlled release etc.Fig. 30 Preparation of hollow particles with PNIPAM microgels as the cores.应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOECSP features7. Applicationscolloidal stabilitythree dimensional networksdispersed particlesExternal stimuli(temperature, ionic strength, pH, external stress solvent nature)Drug delivery Optoelectric switchesEnvironmental cleanup Industry Medicine Surface coating othersApplication 应用表面与胶体化学教育部重点实验室应用表面与胶体化学教育部重点实验室Key Laboratory of Applied Chemistry & Colloid Chemistry, MOE8. Conclusion(1)The combination of a core in the center surrounded by the shell seems to have unique properties of both the materials of the core and the shell.(3)Morphological analysis of CSPs is the most important data that can provide detailed information about internal structure which leads to an estimation of their properties.(2)Applications of CSPs are expanding in various areas such as impact modifiers, surface coatings, printing, catalysis, pollution control, sensing, and drug delivery in biomedical applications.(4) NIPAM is the most commonly used monomer to prepare CSPs, due to its high response to the environmental change.(5)The environmental responses of CSPs, such as thermoresponse and pH sensitivity, are the most important characteristic for drug delivery applications.(6)According to the literature, emulsion polymerization seems to be the most used technique to prepare CSPs in different size.应用表面与胶体化学教育部重点实验室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谢谢谢谢