研究生文献汇报.ppt

1、Coreshell polymers: a review,RSC Adv., 2013,3, 15543-15565,Reporter: Rui Niu Jianwu Guo Xiaobo Teng 2013.11.20,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.Applicatio

2、ns 8.conclusion,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. T

3、he 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 d

4、ifferent components, one in principle forms the core and another forms the shell of the particles.,2. Classification,Core shell polymers (CSPs),State,Hydrogels,NIPAM,Non-NIPAM,Conventionalmonomer,Acrylamide derivatives,Size,Nano,Micro,Non-Hydrogels,Non-aqueous,Organic-inorganic,Single,2.1 Coreshell

5、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 biome

6、dical 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.,2.1.1 NIPAM based CSP hydrogels,32,switchable or smart materials, poly (N -isopropylacrylamide PNIPAM) has been

7、 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.,2.1.2 Non-NIPAM CSP hydrogel,non-NIPAM CSPs (conventional monomer ),hydrophilic

8、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,2.2 Non-hydrogel coreshell polymer,Non Hydrogels,Non-aqueous,Organic-inorgan

9、ic,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

10、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,J. Am. Chem. Soc. , 2010 , 132(35), 1221812221,synthesis of new functional materials for light-emitting devices, solar cells, photodetector

11、s , 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. , 20

12、12 ,22 (22), 1137011378.,Used,Inorganicorganic CSPs,butadiene,styrene,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,multi-step,One-stage reaction:

13、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., conse

14、cutive emulsion,Dispersion 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,emulsion pol

15、ymerization : 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,Example Fig. 3 il

16、lustrates 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 copolym

17、ers can be used to produce coreshell type polymer nanospheres via block copolymerization .,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 mono

18、mer 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 gro

19、w through its versatile reaction and its ability to tailor the properties of the emulsion polymer produced.,Emulsion polymerization,semi-batch process,batch process,The most significant difference between batch and semi-batch emulsion polymerization, Semi-batch process allows two types of feed strea

20、m, M ( monomer) feed and E (emulsion) feeds, Batch processes are of limited versatility for producing emulsion and are mainly use in academic research with simple reaction formulations.,Advantage of Semi-bath: (1) Good temperature control with extra cooling of polymerization process. (2) Easy to con

21、trol polymerization rate by keeping process starved. (3) Flexible control of molecular weight. (4) Good polymer composition control.,Example 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

22、(SFEP).,Example 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 polymerizati

23、on (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,Example three,Fig. 7 Schematic representation of the formation of the coreshell NPs by semi-batch emulsion polymerization. Reproduc

24、ed 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-methoxysi

25、lane (MPS).,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 conti

26、nuous phase.,Example,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

27、(4-vinylpyridine) (P4VP)(四乙烯基吡啶).,3.3 Other techniques to prepare coreshell polymers,Example 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.,Example t

28、wo,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-

29、(2-bromopropionyl)oxy) ethyl acrylate)-g-poly ( Nisopropylacrylamide (HPBPEA-g-PNIPAM), via atom transfer radical polymerization (ATRP).,Mu et al. prepared a monodisperse and multilayer coreshell (MMLCS) via surface cross-linking emulsion polymerization.,Example three,Fig. 10 shows the preparation o

30、f 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,Example four,Thermosensitive PStPNIPAM coreshell particles were synthesized using photoemulsion

31、 polymerization technique.,This new synthesis strategy may Produce a thermosensitive shell of PNIPAM networks with more homogeneous cross-linking density.,Example five,5 mol% NIPAM,Kim et al. fabricated monodisperse coreshell microgels based PNIPAM by capillary microfluidic technique.,Used to develo

32、p 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）,4. Development of latex particle morphology of CSP,Affected by many variables,cross-linking,radical

33、penetration,diffusion,processing,polarity of monomers,batch processing,semi-batch processing,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 morp

34、hology (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.,Example one,Example two,Fig. 14. PSt formed a homogeneous shell on u

35、ncross-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.,4.2 Radical penetration and diffusion,Fig. 15 Possible particle morphologies produced fro

36、m 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 tem

37、perature 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

38、.,5. Characterizations,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 mi

39、crogel 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.,Example two,Lee et al. demonstrated that coreshell po

40、ly (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.

41、,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.,Example three,Zhang et al. reported a facile method to create a living in situ gelling system for controlled format

42、ion 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

43、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.,Exampl

44、e 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