Particles containing reversible covalent bonds which may be sequentially formed and broken multiple times

Abstract

The present invention is directed to a particle-containing entity P-(A--B-M).sub.x wherein P is a solid particle attached to at least one polymer M through one or several reversible covalent bonds -A---B-, wherein A and B are functional groups respectively grafted to P and M thus forming the P-(A---B-M).sub.x particle-containing entity with x being greater than or equal to 1, M has a degree of polymerization comprised between 5 and 1000, preferably ranging from 5 to 500, and wherein the reversible covalent bond -A---B- is chosen among an imine, a disulfide, a boronic ester or an acetal. The invention is also directed to a method of preparing this particle-containing entity, a method for sequentially forming and breaking the reversible covalent bond -A---B- in said particle-containing entity P-(A---B-M).sub.x and dispersions comprising same.

Claims

1. A method for sequentially forming and breaking a reversible covalent bond -A---B- in a particle-containing entity P-(A---B-M).sub.x wherein P is a solid particle attached to at least one polymer M through one or several reversible covalent bonds -A---B-, A and B are functional groups respectively grafted to P and M thus forming the P-(A---B-M).sub.x particle-containing entity with x being greater than or equal to 1, M has a degree of polymerization comprised between 5 and 1000 and wherein the reversible covalent bond -A---B- is selected from the group consisting of an imine, a disulfide, a boronic ester or an acetal and wherein one of functional groups A and B comprises an amine function, a hydroxylamine function or an imine function, and the other comprises an aldehyde function, a ketone function or an imine function so that the resulting -A---B- reversible covalent bond is an imine, said method comprising the following steps: attaching the functional group A to the surface of the solid particle P, thereby forming A-functionalized particles P or providing said A-functionalized particles P; attaching the functional group B to a polymer M, thereby forming B-functionalized polymers M or providing said B-functionalized polymers M, and wherein the functional group B is able to form a reversible covalent bond with the functional group A; reacting the A-functionalized particles P with at least one B-functionalized polymer M to form a reversible covalent bond between the functional groups A and B, thereby forming the P-(A---B-M)x; and, breaking the covalent bonds -A---B- that link the A-functionalized particles and the B-functionalized particles.

2. The method according to claim 1, wherein the imine covalent bond can be broken by acid hydrolysis or by reaction with a competitor molecule C carrying at least one of the following functional groups: primary amine, hydroxylamine, aldehyde, ketone or imine.

3. A method for sequentially forming and breaking a reversible covalent bond -A---B- in a particle-containing entity P-(A---B-M).sub.x wherein P is a solid particle attached to at least one polymer M through one or several reversible covalent bonds -A---B-, A and B are functional groups respectively grafted to P and M thus forming the P-(A---B-M).sub.x particle-containing entity with x being greater than or equal to 1, M is a linear, branched, hyperbranched, grafted, comb-like, star-like, cyclic, a homopolymer, a block copolymer, a random copolymer, a gradient copolymer, an alternating copolymer or a multiblock copolymer and has a degree of polymerization comprised between 5 and 1000 and wherein the reversible covalent bond -A---B- is selected from the group consisting of an imine, a disulfide, a boronic ester or an acetal and wherein one of functional groups A and B comprises an amine function, a hydroxylamine function or an imine function, and the other comprises an aldehyde function, a ketone function or an imine function so that the resulting -A---B- reversible covalent bond is an imine, said method comprising the following steps: attaching the functional group A to the surface of the solid particle P, thereby forming A-functionalized particles P or providing said A-functionalized particles P; attaching the functional group B to a polymer M, thereby forming B-functionalized polymers M or providing said B-functionalized polymers M, and wherein the functional group B is able to form a reversible covalent bond with the functional group A; reacting the A-functionalized particles P with at least one B-functionalized polymer M to form a reversible covalent bond between the functional groups A and B, thereby forming the P-(A---B-M)x; breaking the covalent bonds -A---B- that link the A-functionalized particles and the B-functionalized particles; and recovering the A-functionalized particles P after the breaking of the covalent bond(s) -A---B- by physical separation.

4. A method, for sequentially forming and breaking a reversible covalent bond -A---B- in a particle-containing entity P-(A---B-M).sub.x wherein P is a solid particle attached to at least one polymer M through one or several reversible covalent bonds -A---B-, A and B are functional groups respectively grafted to P and M thus forming the P-(A---B-M).sub.x particle-containing entity with x being greater than or equal to 1, M has a degree of polymerization comprised between 5 and 1000 and wherein the reversible covalent bond -A---B- is selected from the group consisting of an imine, a disulfide, a boronic ester or an acetal wherein the polymer M is a stabilizing agent capable of dispersing the particle P in a medium and the particles P are pigments selected from the group consisting of TiO.sub.2, Cr.sub.2O.sub.3, Fe.sub.2O.sub.3,Fe.sub.3O.sub.4 anthraquinones, phthalocyanines, perylene, quinacridone or indigoid, said method comprising the following steps: attaching the functional group A to the surface of the solid particle P, thereby forming A-functionalized particles P or providing said A-functionalized particles P; attaching the functional group B to a polymer M, thereby forming B-functionalized polymers M or providing said B-functionalized polymers M, and wherein the functional group B is able to form a reversible covalent bond with the functional group A; reacting the A-functionalized particles P with at least one B-functionalized polymer M to form a reversible covalent bond between the functional groups A and B, thereby forming the P-(A---B-M)x; and, breaking the covalent bonds -A---B- that link the A-functionalized particles and the B-functionalized particles.

Description

EXAMPLES

Preparation of Dispersions of A-functionalized Particles in Media Containing B-functionalized Polymers

Examples 1-31

(1) The purpose of these examples is to illustrate the dispersability of A-functionalized particles in solutions containing B-functionalized polymers as compared to pure solvent solutions. These examples illustrate dispersions obtained by the present invention.

(2) For examples 1-31, a two step reaction sequence was followed, as shown in equation 1. In the first step, chemical groups A were attached to the surface of particles P, thereby forming the A-functionalized particles P (examples 1-2). In a subsequent step, the A-functionalized particles P were dispersed in a medium S containing B-functionalized polymers M. Particles were dispersed in the medium as the P-(A---B-M).sub.x entity (examples 3-10 and 17-24). The scheme below is meant to be illustrative but not limiting. In contrast, and to illustrate particles dispersion of the present invention, A-functionalized particles P we dispersed in a pure medium S (examples 10-16 and 25-31).

(3) ##STR00001##

(4) Examples are given below for P=multiwall carbon nanotubes (MWCNT) and Stöber silica (SiO.sub.2), A=benzaldehyde (ald), B=primary amine (NH.sub.2), M=polystyrene (PS), poly(propylene oxide-ethylene oxide) (PPO/PEO), and poly(ethylene glycol) (PEG), and S=cyclohexane, toluene, chloroform, acetonitrile, N,N-dimethyformamide (DMF), ethyl alcohol, and water.

Preparation of Benzaldehyde-functionalized Particles (P=MWCNT and SiO2, A=benzaldehyde)

Examples 1-2

(5) The following general procedure was followed for preparing benzaldehyde-functionalized particles.

(6) Particles P (5 mmol) were dispersed in 50 mL of water by ultrasonication (1 h) then isoamyl nitrite (10 mmol) and 3-aminobenzaldehyde ethylene acetal (10 mmol) were added to the mixture. The reacting media was then heated to 80° C. under vigorous agitation for 24 h. The resultant mixture was cooled down to room temperature and most of the water was then evaporated under vacuum. 50 mL of DMF were added and the benzaldehyde-functionalized particles were filtered on a PTFE membrane and washed until the filtrate became clear. The resulting powder was dried under vacuum overnight.

(7) TABLE-US-00001 exam- Molar ratio ples particle (P:isomaylnitrite:A) Work up 1 MWCNT, Graphistrength 1:2:2 water, C100 (Arkema) 80° C. 2 Stöber silica 1:2:2 water, 80° C.

Preparation of Dispersions of Benzaldehyde-functionalized MWCNT in Different Solvents S Containing Amino-functionalized Polymers (P=MWCNT, A=Benzaldehyde, B═NH2, M=PS, PPO/PEO, S=Cyclohexane, Toluene, Chloroform, Acetonitrile, DMF, Ethyl Alcohol, Water)

Examples 3-16

(8) The purpose of these examples is to illustrate the dispersability of benzaldehyde-functionalized MWCNT in solutions of amino-functionalized polymers as compared to pure solvent solutions.

(9) The following general procedure was followed for preparing dispersions of benzaldehyde-functionalized MWCNT (MWCNT-ald).

(10) 0.05 wt. % MWCNT-ald were dispersed by ultrasonication (150 W, 30 min) in 0.05-0.15 wt. % NH.sub.2-polymer M solutions (examples 3-9) or in pure solvents (examples 10-16). Dispersions were allowed to stand 24 hours and observed using a Leica Leitz DM RD light microscope containing a calibrated ocular lens (10×/0.30 PH1). Absence of aggregates bigger than 10 μm indicates a stable dispersion of MWCNT-ald. Results are set in table 1.

(11) TABLE-US-00002 TABLE 1 exam- MWCNT-ald NH.sub.2—M medium S aggregates > ples (g) (g) (g) 10 μm 3 0.005 0.012 9.983 none PS—NH.sub.2 cyclohexane 4 0.005 0.012 9.983 none PS—NH.sub.2 toluene 5 0.005 0.012 9.983 none PS—NH.sub.2 chloroform 6 0.005 0.007 9.983 none PPO/PEO-NH.sub.2 acetonitrile 7 0.005 0.007 9.983 none PPO/PEO-NH.sub.2 DMF 8 0.005 0.007 9.983 none PPO/PEO-NH.sub.2 ethyl alcohol 9 0.005 0.007 9.983 none PPO/PEO-NH.sub.2 water 10 0.005 9.995 yes cyclohexane 11 0.005 9.995 yes toluene 12 0.005 9.995 yes chloroform 13 0.005 9.995 none acetonitrile 14 0.005 9.995 none DMF 15 0.005 9.995 yes ethyl alcohol 16 0.005 9.995 yes water

(12) These examples show that stable, conventional dispersions can be prepared with benzaldehyde-functionalized MWCNT and amino-functionalized polymers M in a good solvent of the amino-functionalized polymers M, thanks to the imine reversible covalent bond that is formed by reaction between benzaldehyde and amine functions.

(13) Benzaldehyde-functionalized MWCNT aggregate in absence of amino-functionalized polymers M, except in DMF and acetonitrile, which are both polar aprotic solvents that can solubilize the benzaldehyde functions attached onto MWCNT.

Preparation of Dispersions of Benzaldehyde-functionalized Silica Particles in Different Solvents S Containing Amino-functionalized Polymers M (P═SiO2, A=Benzaldehyde, B═NH2, M=PS, PPO/PEO, PEG, S=Cyclohexane, Toluene, Chloroform, Acetonitrile, DMF, Ethyl Alcohol, Water)

Examples 17-31

(14) The purpose of these examples is to illustrate the dispersability of benzaldehyde-functionalized silica particles in solution of amino-functionalized polymers M as compared to pure solvent solutions.

(15) The following general procedure was followed for preparing stable dispersions of benzaldehyde-functionalized silica particles (SiO.sub.2-ald).

(16) 0.05 wt. % SiO.sub.2-ald were dispersed by ultrasonication (150 W, 30 min) in 0.05-0.15 wt. % NH.sub.2-polymer M solutions (examples 17-24) or in pure solvents (examples 25-31). Dispersions were allowed to stand 24 hours and observed using a Leica Leitz DM RD light microscope containing a calibrated ocular lens (10×/0.30 PH1). Absence of aggregates bigger than 10 μm indicates a stable dispersion of SiO.sub.2-ald. Results are set in table 2.

(17) TABLE-US-00003 TABLE 2 exam- SiO.sub.2-ald NH.sub.2—M medium S aggregates > ples (g) (g) (g) 10 μm 17 0.005 0.01 9.985 none PPO/PEO-NH.sub.2 cyclohexane 18 0.005 0.01 9.985 none PS—NH.sub.2 toluene 19 0.005 0.012 9.985 none PS—NH.sub.2 chloroform 20 0.005 0.01 9.985 none PPO/PEO-NH.sub.2 acetonitrile 21 0.005 0.01 9.985 none PPO/PEO-NH.sub.2 DMF 22 0.005 0.01 9.985 none PPO/PEO-NH.sub.2 ethyl alcohol 23 0.005 0.01 9.985 none PPO/PEO-NH.sub.2 water 24 0.005 0.01 9.985 none PEG-NH.sub.2 water 25 0.005 9.995 yes cyclohexane 26 0.005 9.995 some toluene 27 0.005 9.995 some chloroform 28 0.005 9.995 none acetonitrile 29 0.005 9.995 none DMF 30 0.005 9.995 some ethyl alcohol 31 0.005 9.995 yes water

(18) These examples show that stable, conventional dispersions can be prepared with benzaldehyde-functionalized silica particles and amino-functionalized polymers M in a good solvent of the amino-functionalized polymer, thanks to the imine reversible covalent bond that is formed by reaction between benzaldehyde and amine functions. Benzaldehyde-functionalized silica particles form big aggregates in absence of amino-functionalized polymers M in cyclohexane and water, which are apolar aprotic and polar protic solvent, respectively, that cannot solubilize the benzaldehyde functions attached onto silica particles. Some small aggregates (around 10 μm) of benzaldehyde-functionalized silica particles are observed in toluene, chloroform and ethyl alcohol.

Aggregation of A-functionalized Particles in Media Containing B-functionalized Polymers by Breaking the Reversible Covalent Bonds -A---B- that Link the A-functionalized Particles P and the B-functionalized Polymers M and Subsequent Re-dispersions

Examples 32-42

(19) The purpose of these examples is to illustrate the controlled aggregation of A-functionalized particles in solutions of B-functionalized polymers M by breaking the reversible covalent bonds -A---B- that link the A-functionalized particles P and the B-functionalized polymers M. These examples also illustrate the particles recycling and re-dispersion as described in examples 3-9 and 17-24.

(20) The following general procedure was followed for aggregating benzaldehyde-functionalized particles. The procedure is meant to be illustrative but not limiting. 1 to 3 droplets of mineral or organic acid X were added to a stable dispersion described previously. Aggregation took place within 10 to 30 minutes. Benzaldehyde-functionalized particles were separated from the B-functionalized polymer solutions by centrifugation.

(21) The benzaldehyde-functionalized particles hence recovered could then be re-dispersed in another B-functionalized polymer solution according the procedure described in examples 3-9 and 17-24. Aggregations were macroscopically observed and dispersions were observed using a Leica Leitz DM RD light microscope containing a calibrated ocular lens (10×/0.30 PH1). Absence of aggregates bigger than 10 μm indicates a stable dispersion of benzaldehyde-functionalized particles. All aggregation/re-dispersion procedures were repeated at least twice.

Aggregation of Benzaldehyde-functionalized MWCNT in Toluene Containing Amino-functionalized Polymers (P=MWCNT, A=Benzaldehyde, B═NH2, M=PS, PPO/PEO, S=Toluene) and Re-dispersion in Aqueous Solution Containing Amino-functionalized Polymers

Examples 32-35

(22) These examples illustrate the controlled aggregation of benzaldehyde-functionalized MWCNT in solutions of amino-functionalized polymers by breaking the reversible covalent bonds -A---B- that link the A-functionalized particles P and the B-functionalized polymers M. They also illustrate the particles recycling and re-dispersion as described in examples 3-9.

(23) The following general procedure was followed for aggregating benzaldehyde-functionalized MWCNT. 2 droplets of mineral or organic acid X were added to a stable dispersion of MWCNT-ald in toluene. Aggregation took place within 10 to 30 minutes. Benzaldehyde-functionalized MWCNT were separated from the amino-functionalized polymer solution by centrifugation. The benzaldehyde-functionalized MWCNT hence recovered could then be re-dispersed in another amino-functionalized polymer solution according the procedure described in examples 3-9. Dispersions were observed using a Leica Leitz DM RD light microscope containing a calibrated ocular lens (10×/0.30 PH1). Absence of aggregates bigger than 10 μm indicates a stable dispersion of benzaldehyde-functionalized MWCNT). Aggregations were macroscopically observed. All aggregation/re-dispersion procedures were repeated at least twice. Results are set in table 3.

(24) TABLE-US-00004 TABLE 3 number of total re- exam- Dispersion droplets, aggregation time dispersion aggregates > ples NH.sub.2—M/S X acid aggregation (min) NH.sub.2—M/S 10 μm 32 0.07 wt % 2 yes 20 0.07 wt % none NH.sub.2—PPO/PEO HCl NH.sub.2—PEG toluene 37% water 33 0.07 wt % 2 yes 20 NH.sub.2—PPO/PEO PTSA toluene 34 0.07 wt % 2 yes 20 0.07 wt % none NH.sub.2—PS HCl NH.sub.2—PPO/PEO toluene 37% water 35 0.07 wt % 2 yes 20 NH.sub.2—PS PTSA toluene PTSA: para-toluenesulfonic acid

(25) These examples show that stable dispersions of benzaldehyde-functionalized multiwall carbon nanotubes in solution of amino-functionalized polymer can be aggregated by breaking the imine reversible covalent bonds -A---B- that link the A-functionalized particles P and the B-functionalized polymers M, by acid hydrolysis. Benzaldehyde-functionalized MWCNT can be recovered and re-dispersed in others solvents in the presence of soluble amino-functionalized polymers M.

Aggregation of Benzaldehyde-functionalized Silica Particles in Solvent S Containing Amino-functionalized Polymer and Re-dispersion in Solution of Amino-functionalized Polymers M(P═SiO2, A=Benzaldehyde, B═NH2, M=PS, PPO/PEO, PEG, S=Cyclohexane, Toluene, Water)

Examples 36-42

(26) These examples illustrate the controlled aggregation of benzaldehyde-functionalized silica particles in solutions of amino-functionalized polymers M by breaking the reversible covalent bonds -A---B- that link the A-functionalized particles P and the B-functionalized polymers M-. They also illustrate particles recycling and re-dispersion as described in examples 17-24.

(27) The following general procedure was followed for aggregating benzaldehyde-functionalized silica particles. 1 to 3 droplets of HCl 37% were added to a stable dispersion described previously. Aggregation took place within 1 to 30 minutes. Benzaldehyde-functionalized silica particles were separated from the amino-functionalized polymer solutions by centrifugation. The benzaldehyde-functionalized silica particles hence recovered could then be re-dispersed in another amino-functionalized polymer solution according to the procedure described in examples 17-24. Dispersions were observed using a Leica Leitz DM RD light microscope containing a calibrated ocular lens (10×/0.30 PH1). Absence of aggregates bigger than 10 μm indicates a stable dispersion of benzaldehyde-functionalized silica particles. Aggregations were macroscopically observed. All aggregation/re-dispersion procedures were repeated at least twice. Results are set in table 4.

(28) TABLE-US-00005 TABLE 4 number of total re- exam- Dispersion droplets aggregation time dispersion aggregates > ples NH.sub.2—M/S HCl 37% aggregation (min) NH.sub.2—M/S 10 μm 36 0.1 wt % 3 yes 20 0.1 wt % none NH.sub.2—PPO/PEO NH.sub.2—PEG cyclohexane water 37 0.1 wt % 3 yes 20 0.1 wt % none NH.sub.2—PEG NH.sub.2—PS water toluene 38 0.1 wt % 2 yes 30 NH.sub.2—PEG water 39 0.1 wt % 1 yes 30 NH.sub.2—PEG water 40 0.1 wt % 3 yes 20 NH.sub.2—PPO/PEO water 41 0.1 wt % 2 yes 30 NH.sub.2—PPO/PEO water 42 0.1 wt % 1 yes 30 NH.sub.2—PPO/PEO water

(29) These examples show that stable dispersions of benzaldehyde-functionalized silica particles in solution of amino-functionalized polymers M can be aggregated by breaking the imine reversible covalent bonds -A---B- that link the A-functionalized particles P and the B-functionalized polymers M, by acid hydrolysis. Benzaldehyde-functionalized silica particles can be recovered and re-dispersed in others solvents in the presence of soluble amino-functionalized polymers M. These examples also illustrate that aggregation time is correlated to acid quantity, and that acid can be added in catalytic amount to trigger imine function breaking and thereby aggregation of benzaldehyde-functionalized silica particles.

Temperature Controlled Aggregation and Re-dispersions of A-functionalized Particles in Solvent S Containing B-functionalized Polymers M in Theta-conditions (P=MWCNT, SiO2, A=Benzaldehyde, B═NH2, M=PS, PPO/PEO, S=Cyclohexane, Water)

Examples 43-46

(30) The purpose of these examples is to illustrate the controlled aggregation/dispersion process of A-functionalized particles in a solution of B-functionalized polymers by changing the temperature, when solvent/polymer M couple exhibits an upper critical solution temperature or a lower critical solution temperature.

(31) The following general procedure was followed for aggregating benzaldehyde-functionalized particles. The procedure is meant to be illustrative but not limiting.

(32) A stable dispersion at a temperature T1 was heated or cooled to a temperature T2. Aggregation was macroscopically observed. The non-homogeneous solution was then cooled or heated to temperature T1, under stirring or ultrasonication. Re-dispersion was observed using Leica Leitz DM RD light microscope containing a calibrated ocular lens (10×/0.30 PH1). Absence of aggregates bigger than 10 μm indicates a stable dispersion of P-(A---B-M).sub.x entities. All aggregation/re-dispersion procedures were repeated at least twice.

Temperature Controlled Aggregation and Re-dispersions of Benzaldehyde-functionalized Particles in Cyclohexane Containing Amino-functionalized Polystyrene (P=MWCNT, SiO2, A=Benzaldehyde, B═NH2)

Examples 43-44

(33) The couple cyclohohexane/polystyrene exhibits an upper critical solution temperature. This means that there is a temperature theta at which polystyrene is no longer soluble (theta=31-33° C.) in cyclohexane. A stable dispersion of benzaldehyde-functionalized particles in presence of amino-functionalized polystyrene in cyclohexane was heated to 50° C. When cooled to 0-5° C., aggregation occurred within 10-30 minutes. When re-heated to 50° C., re-dispersion occurred within 10-120 minutes under stirring or ultrasonication.

(34) Aggregation was macroscopically observed and re-dispersions were also observed using a Leica Leitz DM RD light microscope containing a calibrated ocular lens (10×/0.30 PH1). Absence of aggregates bigger than 10 μm indicates a stable dispersion of P-(A---B-M).sub.x entities. All aggregation/re-dispersion procedures were repeated at least twice.

(35) TABLE-US-00006 total re- aggregation tempera- dispersion tempera- dispersion ture and time ture and time aggregates > Ex. NH.sub.2—M/S particle (min) aggregation (min) 10 μm 43 0.1 wt % 0.05 wt % 5° C. yes 50° C. none NH.sub.2—PS MWCNT 120  5 cyclohexane 44 0.1 wt % 0.05 wt % 0° C. yes 50° C. none NH.sub.2—PS SiO.sub.2  10 10 cyclohexane

Temperature Controlled Aggregation and Re-dispersions of Benzaldehyde-functionalized Particles in Water Containing Amino-functionalized PPO/PEO (P=MWCNT, SiO2, A=benzaldehyde, B═NH2)

Examples 45-46

(36) The couple water/poly(propylene oxide-ethylene oxide) (Jeffamine® M2005) exhibits a lower critical solution temperature This means that there is a temperature theta at which poly(propylene oxide-ethylene oxide) is no longer soluble (theta=18° C.). A stable dispersion of benzaldehyde-functionalized particles in presence of amino-functionalized poly(propylene oxide-ethylene oxide) in water was cooled to 0-5° C. When heated to 50° C., aggregation occurred within 10-120 minutes. When re-cooled to 0-5° C., re-dispersion occurred within 10-120 minutes under stirring or ultrasonication. Aggregations were macroscopically observed and re-dispersions were also observed using a Leica Leitz DM RD light microscope containing a calibrated ocular lens (10×/0.30 PH1). Absence of aggregates bigger than 10 μm indicates a stable dispersion of P-(A---B-M).sub.x entities. All aggregation/re-dispersion procedures were repeated at least twice.

(37) TABLE-US-00007 total re- aggregation tempera- dispersion tempera- exam- dispersion ture and time ture and time aggregates > ples NH.sub.2—M/S particle (min) aggregation (min) 10 μm 45 0.1 wt % 0.05 wt % 50° C. yes 5° C. none NH.sub.2—PPO/PEO MWCNT 120  5 water 46 0.1 wt % 0.05 wt % 50° C. yes 0° C. none NH.sub.2—PPO/PEO SiO.sub.2  30 10 water

(38) These examples show that stable dispersions of benzaldehyde-functionalized particles in solution of amino-functionalized polymers M can be aggregated and re-dispersed by changing the temperature, when solvent is a theta-solvent of the polymer. They also illustrate that temperature has no effect on the reversibility of the imine reversible covalent bond.

Aggregation of Stable Dispersion of A-functionalized Particles by Addition of a Competitor C that can Break the Reversible Covalent Bonds -A---B- that Link the A-functionalized Particles and the B-functionalized Polymers M (P═SiO2, A=Benzaldehyde, B═NH2, C=Benzaldehyde, NH2-PEG)

Examples 47-48

(39) The purpose of these examples is to illustrate the controlled aggregation of A-functionalized particles in solutions of B-functionalized polymers M by addition of a competitor molecule or polymer C that can break the reversible covalent bonds -A---B- of P-(A---B-M).sub.x entities. C is able to form the same kind of reversible covalent bond as A and B, and thus compete either with A (example 47) or with B (example 48).

(40) The following general procedure was followed for aggregating benzaldehyde-functionalized particles. The procedure is meant to be illustrative but not limiting. To a stable dispersion of 0.05 wt % benzaldehyde-functionalized silica particles was added 1-5 wt % of a competitor C which is not a stabilizing agent in the solvent. Aggregation was macroscopically observed within few seconds to 5 minutes.

(41) TABLE-US-00008 total exam- dispersion competitor aggrega- aggrega- ples NH.sub.2—M/S molecule C tion time tion 47 0.1 wt % NH.sub.2-PEG 5 wt % few seconds yes water benzaldehyde 48 0.1 wt % NH.sub.2-PPO/ 1 wt % 5 minutes yes PEO cyclohexane NH.sub.2-PEG

(42) These examples show that stable dispersions of benzaldehyde-functionalized silica particles in solution of amino-functionalized polymer can be aggregated by breaking the imine reversible covalent bond with a competitor of either benzaldehyde, amine or imine functions. Competitor C is not a stabilizing agent in the considered medium.

Aggregation of Stable Dispersions of A-functionalized Particles in Theta Conditions and Re-dispersion by Addition of a Competitor C that is Soluble in the Same Conditions (P=SiO2, A=Benzaldehyde, B═NH2, Y═NH2-PEG)

Examples 49

(43) The following general procedure was followed for aggregating and re-dispersing benzaldehyde-functionalized particles. The procedure is meant to be illustrative but not limiting.

(44) The couple water/poly(propylene oxide-ethylene oxide) (Jeffamine® M2005) exhibits a lower critical solution temperature This means that there is a temperature theta at which poly(propylene oxide-ethylene oxide) is no longer soluble (theta=18° C.). A stable dispersion of benzaldehyde-functionalized silica particles in presence of amino-functionalized poly(propylene oxide-ethylene oxide) in water was cooled to 0-5° C. 1 wt % of NH.sub.2-PEG was added at 0° C. and the mixture was then heated to 50° C. No aggregation of silica particles was observed while the free amino functional PPO/PEO polymers collapse as a viscous liquid.

(45) This example shows that aggregates of benzaldehyde-functionalized silica particles in a given solvent can be re-dispersed by exchanging a non stabilizing amino-functionalized polymer M with a stabilizing amino-functionalized polymer M.