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WO2008009997A1 - Procédé de polymérisation - Google Patents

Procédé de polymérisation Download PDF

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Publication number
WO2008009997A1
WO2008009997A1 PCT/GB2007/050430 GB2007050430W WO2008009997A1 WO 2008009997 A1 WO2008009997 A1 WO 2008009997A1 GB 2007050430 W GB2007050430 W GB 2007050430W WO 2008009997 A1 WO2008009997 A1 WO 2008009997A1
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WIPO (PCT)
Prior art keywords
fluid
optionally substituted
polymer
group
raft
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PCT/GB2007/050430
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English (en)
Inventor
Steven Melvin Howdle
Kristofer James Thurecht
Wenxin Wang
Andrew Mark Gregory
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The University Of Nottingham
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Publication of WO2008009997A1 publication Critical patent/WO2008009997A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/10—Esters
    • C08F20/12—Esters of monohydric alcohols or phenols
    • C08F20/14—Methyl esters, e.g. methyl (meth)acrylate
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C08F220/12—Esters of monohydric alcohols or phenols
    • C08F220/14—Methyl esters, e.g. methyl (meth)acrylate
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F4/00—Polymerisation catalysts
    • C08F4/04—Azo-compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2438/00—Living radical polymerisation
    • C08F2438/03—Use of a di- or tri-thiocarbonylthio compound, e.g. di- or tri-thioester, di- or tri-thiocarbamate, or a xanthate as chain transfer agent, e.g . Reversible Addition Fragmentation chain Transfer [RAFT] or Macromolecular Design via Interchange of Xanthates [MADIX]

Definitions

  • This invention relates to a process for the production of well defined spherical polymer and copolymer beads, on the micrometer scale, of uniform size (monodisperse microspheres).
  • the molecular architecture of the beads can be controlled to a great extent using a reversible addition fragmentation chain transfer (RAFT) agent.
  • Additional features of the invention relate to the process of in-situ cleavage of the RAFT terminal end groups and purification of the polymer using supercritical fluids.
  • Polymer microspheres have a range of applications including paints, toner, pigments, films, drug delivery devices, car tyres and cosmetics.
  • Polymers are chains of repeating units called monomers.
  • the types of monomers used and how they link together can produce an enormous variety of different types of polymeric product. If more than one type of monomer is used the product is described as a co-polymer.
  • the architecture of the final (co)polymer product is dependent on the types of monomers used, how these monomers are linked together and how long the chains are. If the chains are of varying lengths the (co)polymer is said to be polydisperse. Ideally, the (co)polymer chains should be of similar lengths, i.e. monodisperse, which yields a (co)polymer with uniform morphology and physical properties.
  • the molecular weight and therefore chain length of a polymer can be controlled by judicious choice of an agent used to mediate the polymerisation, of which there are several. These agents can control the rate of the initiation, addition (propagation) and termination steps that ultimately determine the polydispersity of the (co)polymer produced.
  • Controlled/living polymerisations are superior to conventional polymerisation methodologies because they allow greater control of the rate of monomer addition to the growing polymer chain. Controlled/living polymerisations also ensure that the polymer chains grow at the same rate, producing chains that are of the same length (a polymer with low polydispersity). Control over the rate of monomer addition gives the polymer manufacturer the ability to produce polymers with well- defined molecular weights. In addition, this increased degree of control also allows the polymer producer to manipulate the architecture of the final polymer product.
  • Living polymerisations controlled by RAFT Reversible Addition Fragmentation chain Transfer
  • RAFT Reversible Addition Fragmentation chain Transfer
  • the resulting (co)polymers are free from metal impurities which are present in other controlled/living polymerisation methods such as Catalytic Chain Transfer Polymerisation and Atom Transfer Radical Polymerisation.
  • Dispersion polymerisation is a technique used to obtain monodisperse (co)polymer microspheres in the size range from 500 nm to 50 ⁇ m in diameter.
  • a dispersion polymerisation is a method of polymerisation where the monomer is soluble in the media (usually a volatile organic based solvent) but the growing polymer chains become insoluble, once a certain molecular weight is achieved.
  • the growing chains are separated and dispersed throughout the media by employing a dispersant or surfactant.
  • a near critical or supercritical fluid for example carbon dioxide (scCO 2 )
  • scCO 2 carbon dioxide
  • efficient polymerisations to be conducted provided that an appropriate stabiliser/surfactant is used.
  • the present disclosure relates to a process for preparing a polymer using a fluid in its supercritical or near critical state as a dispersing phase for conducting dispersion polymerizations in the presence of a stabilising agent which functions to ensure partition between the growing polymer chain and the fluid which contains unreacted monomer, the process comprising the steps of: i) adding an initiator, a RAFT agent and a stabilising agent to a sealable pressure vessel, ii) adding a first monomer to the pressure vessel, iii) sealing the vessel and introducing the fluid used as a dispersing phase, iv) raising the temperature and/or pressure of the vessel so that the fluid is in a near critical or supercritical state and maintaining this condition for a first period of time, v) optionally introducing a second monomer to the pressure vessel whilst maintaining the fluid in a near critical or supercritical state and maintaining this condition for a second period of time, and vi) returning the sealed vessel to ambient conditions of temperature and pressure to separate the reactant from the fluid.
  • a process for preparing a polymer using a fluid in its supercritical or near critical state as a dispersing phase for conducting dispersion polymerizations in the presence of a stabilising agent comprising the steps of: i) adding a RAFT agent and optionally a stabilising agent to a sealable pressure vessel, and exposing the resulting mixture to an initiator, ii) adding a first monomer to the pressure vessel, iii) sealing the vessel and introducing the fluid used as a dispersing phase, iv) raising the temperature and/or pressure of the vessel so that the fluid is in a near critical or supercritical state and maintaining this condition for a first period of time, v) optionally introducing a second chain extending species to the pressure vessel whilst maintaining the fluid in a near critical or supercritical state and maintaining this condition for a second period of time, and vi) returning the sealed vessel contents to ambient conditions of temperature and pressure to separate the reactant from the fluid.
  • a process for preparing a polymer using a fluid in its supercritical or near critical state as a dispersing phase for conducting dispersion polymerizations in the presence of a stabilising agent comprising the steps of: i) adding a RAFT agent and optionally a stabilising agent to a sealable pressure vessel, and exposing the resulting mixture to an initiator, ii) adding a first monomer and a second chain extending species to the pressure vessel, iii) sealing the vessel and introducing the fluid used as a dispersing phase, iv) raising the temperature and/or pressure of the vessel so that the fluid is in a near critical or supercritical state and maintaining this condition for a first period of time, v) optionally introducing a second initiator to the pressure vessel whilst maintaining the fluid in a near critical or supercritical state and maintaining this condition for a second period of time, and vi) returning the sealed vessel contents to ambient conditions of temperature and pressure to separate the reactant
  • the present invention provides a microsphere having a molecular weight dispersity of less than 1.5, preferably, less than 1.2.
  • the initiator may be any conventional initiator.
  • the initiator is a chemical compound (or compounds), heat or radiation.
  • the initiator may be UV light, gamma radiation, a thermal initiator or a redox initiator.
  • the initiator is azobisisobutylonitrile (AIBN). In another embodiment, the initiator is azobis 4-cyanopentanoic acid (ACP). In another embodiment, the initiator is benzoyl peroxide.
  • the RAFT agent may be any conventional RAFT agent.
  • the process of the present invention is intended specifically to include the use of all RAFT agents described in J. Polym. Sci. Part A: Polym. Chem.: Vol. 43 (2005), 5347-5393 or in WO98/01478.
  • the reader is directed to the above reference for direction as to suitable RAFT agents which can be used in the process of the present invention and these RAFT agents are intended to form part of the present invention.
  • the RAFT agent is a RAFT agent disclosed in the above references.
  • the RAFT agent is a thiocarbonylthio compound e.g. a dithioester, dithiocarbamate, trithiocarbonate or xanthate.
  • the RAFT agent has the following formula:
  • R 1 is hydrogen or is selected from the group comprising: aryl, (C 1 -Cs) ⁇ yI, (C 1 - C 8 )alkoxy, (C 2 -C 8 )alkenyl, (C 2 -C 8 )alkynyl, (C 3 -C 8 )cycloalkyl, (C 1 -C 8 )alkylaryl carbamoyl, di-(Ci-C 8 )alkyl-phosphonato, diaryl-phosphonato, (U-(C 1 -Cs) ⁇ yI- phosphinato, diaryl-phosphinato and -SR 5 , wherein each of the aforementioned groups may be optionally substituted by 1 to 3 substituents, where chemically possible, independently selected from the group comprising: halo, (Q-GOalkyl, hydroxy, cyano, amino and nitro;
  • R 2 and R 3 are each independently selected from the group comprising: hydrogen, (C 1 - Ci 2 )alkyl, (d-Ci 2 )alkoxy, (C 2 -Ci 2 )alkenyl, (C 2 -C 12 )alkynyl, (C 3 -C 8 )cycloalkyl, aryl, and (Ci-C 12 )alkylaryl, wherein each of the aforementioned groups may be optionally substituted by 1 to 5 substituents, where chemically possible, independently selected from the group comprising: halo, (Q-GOalkyl, hydroxyl, cyano, amino, and nitro; R 4 is selected from the group comprising: (Ci-C 12 )alkyl, (C 3 -C 8 )cycloalkyl, aryl, COOH, COOZ, COOR and -CN, where Z is a suitable counter ion and R is (Q-C ⁇ alkyl; and R 5 is hydrogen or is selected from the
  • R 1 is selected from the group comprising: aryl, (Ci-C 8 )alkyl, (C 1 - C 8 )alkoxy, (C 2 -C 8 )alkenyl, (C 2 -C 8 )alkynyl, (C 3 -C 8 )cycloalkyl and (C 1 -C 8 )alkylaryl, wherein each of the aforementioned groups may be optionally substituted by 1 to 3 substituents, where chemically possible, independently selected from the group comprising: halo, (Q-CzOalkyl, hydroxy, cyano, amino and nitro.
  • R 1 is aryl. More preferably, R 1 is phenyl or naphthyl. In an alternative embodiment, R 1 is -SR 5 .
  • R 2 and R 3 are each independently selected from the group comprising: hydrogen, (Ci-C 8 )alkyl, (CrC 8 )alkoxy, (C 2 -C 8 )alkenyl, (C 2 -C 8 )alkynyl, (C 3 - C 8 )cycloalkyl, aryl, and (Ci-C 8 )alkylaryl, wherein each of the aforementioned groups may be optionally substituted by 1 to 3 substituents, where chemically possible, independently selected from the group comprising: halo, (Q-CzOalkyl, hydroxyl, cyano, amino, and nitro.
  • R 2 is hydrogen, optionally substituted (Ci-C 8 )alkyl, (Ci-C 8 )alkoxy or optionally substituted aryl. More preferably, R 2 is hydrogen, optionally substituted (C 1 - CzOalkyl, (Q-CzOalkoxy or optionally substituted aryl. Preferably, R is hydrogen, optionally substituted (C 1 -C 8 ) ⁇ yI, (Q-CsMkoxy or optionally substituted aryl. More preferably, R 3 is hydrogen, optionally substituted (C 1 - C 4 )alkyl, (Q-CzOalkoxy or optionally substituted aryl.
  • R 4 is -CN.
  • R 4 is selected from the group comprising: (Q-Q ⁇ alkyl, (C 3 -Cs)cycloalkyl, aryl, COOH and COOR, where R is (Ci-C 6 )alkyl.
  • R 4 is aryl or COOH.
  • R is optionally substituted (C 1 -C 12 )alkyl or optionally substituted (Ci-Ci 2 )alkoxy.
  • Suitable counter ions include Group IA or Group HA metals with Na and K being preferred.
  • the RAFT agent is ⁇ -cyanobenzyl dithionaphthylate.
  • the RAFT agent has the following formula:
  • the RAFT agent has the following formula:
  • the RAFT agent has the following formula:
  • the RAFT agent has the following formula:
  • the RAFT agent has the following formula:
  • the RAFT agent has the following formula:
  • the stabiliser may be any conventional stabiliser capable of ensuring partition of monomer and polymer.
  • the process of the present invention is intended to include the use of all stabilisers described in J. Eastoe et al., Current Opinion in Colloid and Interface Science, 8, (2003), 267-273. The reader is directed to the above reference for direction as to suitable stabilisers which can be used in the process of the present invention and these stabilisers are intended to form part of the present invention.
  • the stabiliser a species capable of stabilising a free radical polymerisation in CO 2 .
  • the stabiliser is polydimethylsiloxane monomethacrylate (PDMS-MMA).
  • the stabiliser is Krytox TM, which has the following formula:
  • the terms 'stabiliser', 'stabilising agent' and 'surfactant' are used interchangeably and refer to a substance that functions to ensure partition between the growing polymer and the fluid solution containing monomer.
  • the surfactant functions to keep the growing polymer separate from the monomer solution. It is this partitioning of monomer and polymer which enables the polymer to keep growing in the dispersion in the form of spherical particles.
  • the presence of the stabiliser/surfactant is thus important to the efficient functioning of the process.
  • Any conventional polymerisation stabiliser can be used in the process of the present invention.
  • one compound can function as both the RAFT agent and the stabiliser (a macroRAFT agent).
  • the RAFT agent and stabiliser can be part of the same molecule.
  • the process of the present invention is intended to include the use of all combined RAFT agents and stabilisers described in Z. Ma, P. Lacroix- Desmazes, Polymer, 45, 6790, (2004), 6789-6797.
  • the reader is directed to the above reference for direction as to suitable combined RAFT agents and stabilisers which can be used in the process of the present invention and these combined RAFT agents and stabilisers are intended to form part of the present invention.
  • the concentration of the stabiliser can be high and can be up to 50% with respect to the monomer.
  • the vessel is an autoclave.
  • the sealed vessel contents are returned to ambient conditions of temperature and pressure by slow venting or spray collection.
  • the dispersion polymerisation is a controlled dispersion polymerisation.
  • the dispersion polymerisation may be controlled to provided polymers of desired polymer chain length and/or low molecular weight dispersity.
  • the initiato ⁇ RAFT ratio is in the range between 1:20 and 5:1 inclusive. In another embodiment the initiator: RAFT ratio is in the range between 1:5 and 2:1 inclusive. In another embodiment, the initiato ⁇ RAFT ratio is in the range between 1:4 and 2:1 inclusive. In another embodiment, the initiato ⁇ RAFT ratio is in the range between 1:2 and 2:1 inclusive. In another embodiment, it is in the range between 1:1 and 1:2 inclusive.
  • the monome ⁇ RAFT ratio is in the range between 20000:1 and 10:1.
  • the ratio is in the range between 5000:1 and 100:1.
  • the ratio is in the range between 2000:1 and 100:1.
  • the ratio is in the range 2000:1 and 600:1.
  • the ratio is 2000:1.
  • the ratio is 600:1.
  • the stabiliser is present in an amount of between 1 and 50 wt% with respect to the monomer. Preferably, the stabiliser is present in an amount between 2.5 and 10 wt% with respect to the monomer.
  • the chain extending species is a second monomer.
  • the first and second monomer may be the same or different.
  • Many conventional monomers may be used in the process of the present invention. Specific monomers that find application include: acrylamide, acrylate, acrylic acid, acrylonitrile, 1,3 -butadiene, cyanoacrylate, ethyl acrylate, ethylene, ethylene oxide, methacrylic acid, methyl methacrylate, propylene, styrene, vinyl acetate, vinyl chloride and vinylsilane.
  • Particularly preferred monomers are acrylic acid, acrylates, styrenics and derivatives thereof.
  • Other preferred monomers include vinyl monomers used in conventional free-radical polymerisation.
  • the first and second monomer are each independently acrylate monomers.
  • Preferable monomers include methyl methacrylate (MMA), tertiary-butyl acrylate (tBA), methacrylic acid (MA) and styrene.
  • Monomers can be added alone or optionally in combination with a suitable solvent.
  • the fluid used as a dispersing phase is in the supercritical or near critical state.
  • a supercritical fluid is defined as a substance which is above the critical pressure and critical temperature for that substance, but below the pressure required to form a solid.
  • the term “supercritical” is used herein to denote a fluid which is above its critical temperature and pressure.
  • the term “near critical” refers to a fluid which is under conditions of temperature and pressure below its critical point but the conditions of temperature and pressure are such that the density of the fluid is sufficient to ensure that the monomer but not the polymer being formed are substantially in a single phase with said fluid.
  • the reaction will operate in the fluid at temperatures and pressures below the critical point of the fluid being used as the solvent, provided that the density of the, fluid is sufficient to ensure that the monomer is present in the fluid in substantially in a single phase.
  • These conditions are hereafter referred to as being near-critical.
  • the conditions employed will be supercritical i.e. the fluid is at temperature and pressure above its critical point.
  • the conditions of temperature and pressure are above the critical point of the solvent.
  • Particularly favoured media to have in the reaction system as component in a supercritical condition include carbon dioxide, sulphur dioxide, nitrogen, alkanes such as ethane, propane and butane, alkenes, ammonia, and halocarbons (CFCs and HFC's) such as trichlorofluoromethane, dichlorofluoromethane, dichlorodifluoromethane, chlorotrifluoromethane, bromotrifluoromethane, trifluoromethane, and hexafluoroethane.
  • CFCs and HFC's halocarbons
  • the choice of supercritical fluid is only limited by the engineering constraints but particularly favoured fluids are carbon dioxide and nitrogen, and nitrogen is of particular interest.
  • Other fluids such as halocarbons or hydrocarbons or a mixture of fluids could also be used.
  • the fluid may be a mixture of two or more fluids having critical points which do not require commercially unacceptable conditions of temperature and pressure in order to achieve the necessary conditions for reaction according to the present invention.
  • mixtures of carbon dioxide with an alkane such as ethane or propane, or a mixture of carbon dioxide and sulphur dioxide may be employed close to or above their theoretical critical points.
  • Preferred fluids have a good solvating power and are not incompatible with the polymerisation process.
  • Carbon dioxide is particularly preferred on account of its the unique properties.
  • SCFs, and particularly ScCO 2 are described of having properties intermediate of those of a liquid and a gas, i.e. they can behave like solvents and dispersing phases while at the same time being diffuse in nature like a gas.
  • One of the advantages of using a ScCO 2 as a solvent in the process of the present invention is that it enables facile product separation. By simply depressurizing the reaction vessel the ScCO 2 solvent/dispersant simply evaporates and leaves no solvent residue on the product. This is a particular advantage over other polymerisation methods which require further purification by removing the solvent and/or any unreacted monomer.
  • Stabilisers/surfactants suitable for the process of the invention generally have a CO 2 -philic head group and a hydrocarbon chain.
  • Preferred stabilisers/surfactants are fluorinated hydrocarbons or siloxanes.
  • Many stabilisers/surfactants useful in the invention are commercially available.
  • the first period of time is from 1 to 72 hours.
  • the first period of time is from 4 to 72 hours.
  • the first period of time is from 4 to 48 hours.
  • the second period of time is from 1 to 72 hours.
  • the second period of time is from 4 to 72 hours.
  • the second period of time is from 4 to 48 hours.
  • the present invention demonstrates that RAFT mediated dispersion polymerizations can be conducted in ScCO 2 , to yield monodisperse polymer micro-particles with extremely low molecular weight dispersity. This has been done using simple commercially available stabilizers.
  • the polymer exhibits true 'living' character, with the polymer strands growing upon the addition of more monomer and initiator after the original polymerisation has been purified (chain extension). If the polymerisation was not living the addition of monomer and initiator to the purified polymer would yield new polymer chains, rather than the chain extension of the original polymer. This living character results in a polymer which maintains low polydispersity.
  • the advantages of the method of the present invention to produce core-shell particles are several fold: i) The method is a true dispersion technique to yield particles in a specific size range, ii) Improved control over the composition and thickness of the layers of the spheres can be achieved. iii) The process is not limited by monomer choice. iv) Core-shell particles are formed by block copolymerisation rather than blending two distinct polymers together, which enhances stability and versatility.
  • RAFT mediated dispersion polymerisations usually yield coloured products, due to the RAFT terminal groups remaining on the polymer.
  • the colours depend on the RAFT agent used.
  • the present invention overcomes this limitation by facilitating the cleavage of the RAFT terminal end groups from the polymer and purification in-situ to yield colourless polymer particles.
  • FIGURE 1 shows a Scanning Electron Micrograph of particles produced by RAFT mediated dispersion polymerisation conducted in ScCO 2 .
  • the perfectly spherical particles are clearly evident, and
  • FIGURE 2 shows a Transmission Electron Micrograph of the core shell particles.
  • the microtome process has slightly distorted the particles into an oval shape.
  • the shell of the particles can be clearly seen.
  • FIGURE 3 shows the molecular weight of polymer vs. conversion with various RAFT agents ⁇ (1); -* ⁇ (2); ⁇ (3); X (4).
  • Theoretical molecular weight based on RAFT agent concentration is shown in the solid line and theoretical molecular weight based on RAFT agent and AIBN concentrations is shown in the dashed line.
  • FIGURE 4 shows a Scanning Electron Microscopy Image of PMMA particles formed using PDMS-RAFT.
  • the autoclave was sealed, heated to 65 0 C and pressurised to 4000 psi with stirring for 40 hours.
  • Morphology Spherical particles in size range 1-5 microns
  • the autoclave was sealed, heated to 65 0 C and pressurised to 4000 psi with stirring for 40 hours.
  • Example 3 Reaction time: varied for monomer conversion.
  • Entry 7 proves that this is a living polymerisation by chain extension of the original polymer.
  • the original polymer (entry 3) was purified then put it back into the reaction vessel with more monomer and initiator. Proof of living polymerisation is shown by the increase in molecular weight of the original chain, rather than just another polymer growing. Hence, there must be RAFT groups on the end of the original polymer and the new monomer just adds on there, rather than initiating new polymer chains.
  • the polymerisation is performed in a one-pot, two step process. Initially, 3 mL of MMA, 5 wt % stabiliser, AIBN, RAFT ⁇ -cyanobenzyldithiobenzoate and CO 2 is added to a 20 mL autoclave. Reaction proceeds for 2 days at 65 0 C and 4000 psi.
  • Final polymer has PDI ⁇ 1.5 and particulate morphology in range of 1-5 microns.
  • TEM FIG. 2 shows that micro-morphology can be core-shell or phase separated species depending on the conditions of the experiment.
  • This example illustrates the results obtained for the PMMA polymers obtained using RAFT agents (1, 2, 3 and 4) for different reaction times in ScCO 2 according to the process of the present invention.
  • M n is the molecular weight
  • M ntn is the theoretical molecular weight
  • PDI is the polydispersity
  • Example 6 linear molecular weight progression with conversion.
  • Example 7 Targeted molecular weight in ScCO 2 using various concentrations of RAFT agent 3. (Methodology is applicable for a range of molecular weights).
  • Dp is the degree of polymerisation (how many monomer units are incorporated into the polymer chain).
  • Example 8 Targeting lower weight polymers for MALDI-TOF analysis using RAFT agents 3 and 4 (functionalised end-groups - various ratios of [RAFT]: [initiator]).
  • Example 9 Effect of Stabiliser concentration using RAFT agent 3.
  • Example 10 Changing RAFT concentrations and applying to different monomers.
  • Example 11 Polymerisation using macroRAFT agents - combined stabiliser and RAFT agent on the one molecule.
  • [M]: [CTA]: [I] is the ratio of monomer to RAFT agent to initiator concentrations. M th is the theoretical molecular weight based on initiating species. In all cases, azobisisobutyronitrile (AIBN) was used as the initiator.
  • AIBN azobisisobutyronitrile

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Abstract

La présente invention concerne un procédé de préparation d'un polymère par polymérisation en dispersion modulée par des agents RAFT (reversible addition fragmentation chain transfer). L'invention concerne plus spécifiquement un procédé de production de perles de polymère et copolymère sphériques bien définies, à l'échelle micrométrique, de taille uniforme (microsphères monodispersées). L'architecture moléculaire des perles peut être modulée dans une grande mesure en utilisant l'agent RAFT. La présente invention concerne également des microsphères monodispersées présentant une architecture stratifiée unique.
PCT/GB2007/050430 2006-07-21 2007-07-20 Procédé de polymérisation WO2008009997A1 (fr)

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GBGB0614623.7A GB0614623D0 (en) 2006-07-21 2006-07-21 Process for conducting dispersion polymerisations controlled by raft agents in supercritical fluids
GB0614623.7 2006-07-21

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WO2009153162A1 (fr) * 2008-06-17 2009-12-23 Basf Se Procédé de production d'une dispersion aqueuse de polymère
US8252880B2 (en) 2007-05-23 2012-08-28 Carnegie Mellon University Atom transfer dispersion polymerization
CN102702421A (zh) * 2012-06-29 2012-10-03 北京智生阳光新材料科技发展有限公司 一种单分散聚合物功能微球的光化学制备方法
US8865797B2 (en) 2007-05-23 2014-10-21 Carnegie Mellon University Hybrid particle composite structures with reduced scattering
WO2015020512A1 (fr) * 2013-08-06 2015-02-12 Universidad Nacional Autónoma de México Polymères à structure de réseau de faible densité et procédé d'obtention de ceux-ci par polymérisation radicalaire par désactivation réversible dans des fluides comprimés
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CN106188380A (zh) * 2016-08-03 2016-12-07 台州艾斐建材有限公司 一种复合材料包覆表面的龙头
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