CN108503751B

CN108503751B - Preparation and application of quaternary ammonium polymer modified nano starch composite particle material

Info

Publication number: CN108503751B
Application number: CN201810129735.2A
Authority: CN
Inventors: 王彦斌; 苏琼; 王济乾
Original assignee: Northwest Minzu University
Current assignee: Northwest Minzu University
Priority date: 2018-02-08
Filing date: 2018-02-08
Publication date: 2020-09-18
Anticipated expiration: 2038-02-08
Also published as: CN108503751A

Abstract

The invention relates to preparation and application of a quaternary ammonium polymer modified nano starch particle composite material, which takes corn starch as a raw material and prepares highly dispersed nano starch through acid catalysis hydrolysis; then 2-bromine isobutyryl bromide is used as an initiator, triethylamine is used as an acid-binding agent, and the initiator modified nano starch particles are prepared; then, taking the 2-bromoisobutyryl bromide modified nano-starch particles as an initiator, and carrying out polymerization modification on DMAEMA to obtain PDMAEMA modified nano-starch particles; finally, quaternary ammonium modification is carried out to obtain the quaternary ammonium polymer modified nano starch granular material, and the product has good dispersibility, pH value and temperature responsiveness; the quaternary ammonium polymer modified nano-starch composite material prepared by the invention has good adsorption performance on chromate in simulated sewage, and has good application prospect in environmental management; and the modified nano-starch composite material can be used for realizing good pH value and temperature responsiveness.

Description

Preparation and application of quaternary ammonium polymer modified nano starch composite particle material

Technical Field

The invention belongs to the fields of high molecular material technology and environmental management, and particularly relates to a preparation method of a quaternary ammonium polymer modified nano starch particle composite material; the invention also relates to application of the quaternary ammonium polymer modified nano starch particle composite material as an adsorbent in treatment of chromate-containing wastewater.

Background

The corn starch is a natural renewable natural polymer material, has rich sources, good biocompatibility and degradability, wide application, safety and environmental protection, and is easy to modify and prepare various environment-friendly materials. Compared with the inorganic nano reinforcing agent, the natural polymer nano starch microcrystal prepared from the corn starch has the advantages of wide source, low cost, low density and many hydroxyl groups on the surface, and can be functionally modified through graft copolymerization.

In the traditional graft copolymerization process, the concentration of an initiator on the surface of the starch is relatively low, the grafting efficiency is low, and how to introduce more active points on the surface of the starch is critical. The macromolecular chain of the starch has active hydroxyl, which creates conditions for introducing an active initiator. Researches show that the SI-ATRP is used for surface graft polymerization modification of the nano starch material, and can fully exert the characteristics of controllability and activity. Based on the method, an acyl halide compound containing halogen atoms on carbon chains is selected as an initiator of Atom Transfer Radical Polymerization (ATRP), the surface of the nano starch is modified through the reaction of an active end group in the initiator and a hydroxyl group at an active end of a nano starch macromolecule, so that a carbon-halogen functional group capable of carrying out polymerization reaction is introduced into a nano starch side group, and further, vinyl monomers are initiated to be grafted and polymerized onto the surface of the starch, so that the performance of the starch is improved, and the application field of the starch is widened.

Disclosure of Invention

The invention aims to provide a preparation method of a quaternary ammonium polymer modified nano starch particle composite material.

Another object of the invention is to provide the application of the nano starch particle composite material modified by the quaternary ammonium polymer in adsorption treatment of chromate-containing wastewater.

The technical scheme adopted by the invention is as follows: a preparation method of a quaternary ammonium polymer modified nano starch particle composite material comprises the following process steps:

step (1), preparation of nano starch particles: dispersing the corn starch after vacuum drying in 2-4M dilute sulfuric acid, hydrolyzing in an oil bath at 30-40 ℃ for 8-11 days, centrifuging at high speed, and drying to obtain nano starch particles;

step (2) preparation of 2-bromoisobutyryl bromide modified nano-starch particles: using dichloromethane as a solvent, triethylamine as an acid-binding agent and 2-bromoisobutyryl bromide as an initiator, modifying and polymerizing the nano-starch particles prepared in the step (1) at room temperature for 20-24 h under the protection of nitrogen and stirring, centrifuging at a high speed, separating a polymerization product, washing with acetone, and drying to obtain 2-bromoisobutyryl bromide modified nano-starch particles;

step (3) preparation of PDMAEMA modified nano-starch particles: using deionized water as a solvent, using the 2-bromoisobutyryl bromide modified nano-starch particles prepared in the step (2) as an initiator, using 2, 2' -bipyridine and cuprous bromide as a composite catalyst, and carrying out modification polymerization on dimethylaminoethyl methacrylate at 30-40 ℃ under the protection of nitrogen and stirring; after the reaction solution becomes uniform blue transparent solution, centrifuging at high speed, washing the separated polymerization product with acetone, and drying to obtain PDMAEMA modified nano-starch particles;

step (4), preparation of the quaternary ammonium polymer modified nano starch granular material: reacting the PDMAEMA modified nano-starch particles prepared in the step (3) at room temperature in a dark place for 20-24 hours by using nitromethane as a solvent and iodomethane as a quaternizing agent under the protection of nitrogen; and after the reaction is finished, centrifuging at a high speed, washing a separation product by using acetone, and drying to obtain the quaternary ammonium polymer modified nano starch granular material.

Preferably, the drying in step (1) is: freeze drying for 20-24 hr, and vacuum drying at 60-70 deg.C for 20-24 hr.

Preferably, in the step (2), the amount of triethylamine is 0.02-0.03 times of the mass of the nano starch; the dosage of the initiator 2-bromo isobutyryl bromide is 0.05-0.06 time of the mass of the nano starch particles.

Preferably, in the step (3), the amount of the monomer DMAEMA is 0.1-0.3 times of the mass of the 2-bromoisobutyryl bromide modified nano-starch particles.

Preferably, in the step (3), the molar ratio of the composite catalyst 2, 2' -bipyridyl to cuprous bromide is 1: 1-3; the dosage of the composite catalyst is 0.05 to 0.06 time of the molar weight of the monomer DMAEMA.

Preferably, in the step (4), the molar ratio of methyl iodide to the PDMAEMA-modified nano starch particles is 1: 3.0-3.5.

preferably, in the step (4), the amount of nitromethane is 10 to 15 times of the molar amount of methyl iodide.

Preferably, the drying in the steps (2), (3) and (4) is vacuum drying at 60-70 ℃ for 20-24 h.

Preferably, the high-speed centrifugation speed in the steps is 10000-12000 rpm.

Firstly, the synthetic route of the nano starch composite material modified by the quaternary ammonium polymer is as follows:

the invention takes nano starch as a substrate, obtains a compound 1(StNP-I) through surface modification of an initiator, and introduces an active functional group carbon halogen bond of SI-ATRP polymerization reaction, thereby realizing SI-ATRP reaction. The initiator modified nano-starch particles are subjected to SI-ATRP reaction under the action of CuBr and bpy catalysts to modify the DMAEMA monomer to obtain a compound 2(PDMAEMA-StNP), and the polymer modified nano-starch composite material has a core-shell structure, so that the surface physicochemical property of the nano-starch is changed, and the polymer modified nano-starch composite material has a new function. As the monomer of the graft copolymerization reaction has tertiary amine functional group, the compound 3(QPDMAEMA-StNP) can be further obtained through quaternization reaction, so that the surface performance of the nano starch composite material is further modified.

Characterization of quaternized Polymer-modified Nano-starch composites

1. Infrared spectroscopic analysis (FT-IR)

An ENSOR 27instrument (Bruker) infrared spectrometer is adopted to study the characteristic peak of the sample in a transmission mode, the resolution is 4cm < -1 >, and the scanning times are generally 32 times. FIG. 1 shows FT-IR spectra of a starch surface graft polymer (PDMAEMA-StNP) and its raw material (StNP), intermediate (StNP-I) and derivative (QPDMAEMA-StNP). As can be seen, the characteristic peak of the nano starch particle (StNP) at 537cm-1 is a skeleton vibration peak of a pyran type six-membered ring, the characteristic peak at 764cm-1 is a C-C stretching vibration peak, the characteristic peak at 930cm-1 is an alpha-1, 4-glycosidic bond skeleton vibration peak, the characteristic peak at 1067cm-1 is a C (1) -H bending vibration peak, the characteristic peak at 1094cm-1 is a C-O-H bending vibration peak, the characteristic peak at 1163cm-1 is a C-O and C-C stretching vibration peak, the characteristic peak at 1415cm-1 is a CH2 bending vibration peak and a C-O-O stretching vibration peak, the characteristic peak at 2800-3000cm-1 is a CH2 deformation peak, and the characteristic peak at 3000-3600cm-1 is an O-H stretching vibration peak.

After the surface of the nano starch particles is modified by 2-bromo isobutyryl bromide, an absorption peak of-C ═ O stretching vibration appears at 1730cm-1, which shows that esterification reaction is carried out between the 2-bromo isobutyryl bromide and hydroxyl in the starch, and the initiator successfully modifies the surface of the nano starch particles.

The infrared analysis result of PDMAEMA-StNP obtained after graft polymerization shows that the characteristic absorption peak of starch disappears, NH stretching vibration peak appears at 3300-3500cm-1, C-H stretching vibration peak appears at-CH 3 and-CH 2-at 2926cm-1, C-H stretching vibration peak appears at-N (CH3)2 at 2855 and 2770cm-1, the absorption peak intensity of C ═ O stretching vibration corresponding to 1730cm-1 is obviously enhanced because the polymer chain after starch surface graft modification contains a large amount of ester group functional groups, and the existence of polymer is further verified at-CH 2 bending vibration peak corresponding to 1459cm-1 and C-N stretching vibration peak corresponding to 1150cm-1 [17], which shows that the surface of nano starch particle is successfully modified by DMAEM polymer.

The infrared analysis result after quaternization shows that the C-H stretching vibration peak of-CH 2-in-situ at 2926cm-1 is shifted to 3009cm-1 towards high wave number, the absorption peaks originally corresponding to the C-H stretching vibration peaks 2855 and 2770cm-1 in the tertiary amino-N (CH3)2 degenerate into a single peak at 2955cm-1, and the absorption peak of the quaternary ammonium group CH2-N + (CH3)3 appears at 951 cm-1. Thus, QPDMAEMA-StNP nano-starch composite material is proved to be generated.

The infrared analysis result clearly shows that the initiator is successfully grafted on the surface of the nano starch, ATRP polymerization is initiated on the surface, the surface of the nano starch is modified by PDMAEMA, and the preparation of the quaternized polymer modified nano starch particles is successfully realized after quaternization reaction.

2. X-ray diffraction analysis (XRD)

FIG. 2 shows the XRD analysis results of the starch surface graft polymer and the raw material. The comparison shows that after 2-bromoisobutyryl bromide modifies the nano starch particles, the intensity of diffraction peaks is slightly reduced, which indicates that the degree of crystallization of the nano starch is reduced in the modification process of the initiator, but the shapes and positions of the characteristic diffraction peaks are not changed, which indicates that the structure of the nano starch particles is not damaged; the diffraction peak of the starch disappears in the sample modified by grafting copolymerization, and a new broad peak appears at 17.73 degrees, which is the characteristic diffraction peak of the starch surface polymer, and shows that the surface of the starch modified by grafting is basically covered by a polymer chain, so that the nano starch can be endowed with new surface physicochemical properties. The sample obtained after quaternization modification has no obvious diffraction peak, which indicates that the sample has an amorphous structure.

The X-ray diffraction analysis result shows that the initiator successfully modifies the surface of the nano starch, and the surface of the nano starch is basically covered by the polymer after the PDMAEMA graft polymerization, which shows that the preparation of the core-shell structure can be realized by initiating the graft copolymerization reaction on the surface by using the nano starch as a template, the crystallization degree is obviously changed after the quaternization modification, and the application range of the nano starch is further expanded.

3. X-ray photoelectron spectroscopy (XPS)

FIG. 3 is a comparison of XPS survey scan results of products at different stages during the nano starch graft modification process. The comparison shows that after the nano starch particles react with 2-bromoisobutyryl bromide, new peaks appear on surface elements of the starch, after the grafting polymerization, the monomer contains nitrogen elements, so that characteristic peaks of the nitrogen elements appear in a full-spectrum scanning chart, and after the quaternization treatment, the characteristic peaks of the iodine elements appear in the full-spectrum scanning chart due to the introduction of the iodine elements. XPS full spectrum scanning results further verify that the initiator successfully modifies the nano starch particles, the PDMAEMA modifies the nano starch particles and the quaternization process.

FIG. 4 shows the peak results of C1s spectrum of product samples at different stages in the nano starch graft modification process. FIG. 4a shows the C1s peak profile of StNP sample. The results show that the binding energy is 283.268eV and 284.695eV, which correspond to peaks of C-C chain and-CH 2OH side chain carbon elements in the pyranose ring, respectively, the peak of carbon element with binding energy of 285.592eV corresponds to the peak of carbon element of C-O bond in the pyranose ring, and the ratio of O to C element is 0.52; FIG. 4b shows the result of C1s spectrum peak of nano starch modified by initiator, and the result shows that binding energy is 283.268eV and 284.127eV, which correspond to the peaks of C-C chain and C-CH 2OH side chain carbon elements in pyranose ring, the most intense peak binding energy is 285.101eV, which corresponds to the peak of carbon element in C-Br bond in initiator, the peak of carbon element with 286.899eV, which corresponds to the peak of carbon element in-O-C-O bond, the ratio of O to C element is 0.440874, compared with the nano starch, the surface composition is reduced due to the grafting reaction of initiator and nano starch particle surface, thereby causing the change of surface composition; FIG. 4C shows the peak separation of the C1s spectrum of the PDMAEMA-StNP sample. The binding energies of 281.926eV and 284.002eV correspond to the peak of C element in C-C chain, the peak of carbon element of 284.772eV corresponds to the peak of carbon element in CO bond, and the most intense binding energy of the peak of 285.802eV corresponds to the peak of carbon element in C-N bond, respectively. The peak of carbon element with binding energy of 279.609eV corresponds to the peak of quaternary carbon element, the peak of carbon element with binding energy of 288.570eV corresponds to the peak of carbon element in O-C ═ O bond, the atomic ratio of N to C is about 0.098936, which is close to the atomic ratio of N to C of 0.125 in DMAEMA molecule, which indicates that the surface of polymer modified nano starch is coated by polymer, consistent with the results of the foregoing infrared characterization; fig. 4d shows the results of the C1s spectral peak splitting for the QPDMAEMA-StNP sample, with binding energies of 284.801eV corresponding to the C element peak in the C-C chain, the carbon element peak of 284.953eV corresponding to the carbon element peak in the CO bond, the most intense peak binding energy of 285.903eV corresponding to the carbon element peak in the C-N bond, the carbon element peak of 288.295eV corresponding to the carbon element peak in the-O-C ═ O bond, and the atomic ratio of carbon element to oxygen element of 0.27492, very close to the elemental ratio of the polymer monomers, indicating that the surface of the nano-starch is substantially coated by the polymer. The atomic ratio of N to C is about 0.098936, the atomic ratio of I to C is about 0.069354, the atomic ratio of I to N is about 0.7:1, and the nano starch surface graft polymer has complete indication quaternization degree.

FIG. 5 shows a comparison of XPS analysis results of surface N elements of modified nano-starch, and analysis shows that the binding energy of tertiary N in the graft polymer on the surface of the nano-starch particle is 399.22eV, and the binding energy of quaternary N in a QPDMAEMA-StNP sample obtained after quaternization is 402.1333eV, which indicates that quaternization modification increases the binding energy of tertiary N due to the increase of charge of quaternary N.

4. Nuclear magnetic resonance

FIG. 6 shows the results of 1H NMR analyses of StNP (a), StNP-I (b), PDMAEMA-StNP (C) and QPDMAEMA-StNP (d), and a comparison of a and b revealed that the chemical shifts 0.9ppm were proton peaks in-OH, 2.14 to 3.49ppm were proton peaks of C4, C2 and C3 in starch, 3.9ppm was a proton peak of C5, and 4.2 to 4.3 ppm were a proton peak of C1; in the two figures, the proton peak shift of the raw material nano starch particles is unchanged, but new proton peaks appear at the positions of chemical shifts of 0.7ppm and 1.3ppm, which indicates that the 2-bromoisobutyryl bromide is successfully modified, and a starch chain is not changed; comparing c and d, the proton peaks of the monomers appear at the chemical shifts of 1.2, 1.9, 2.1, 2.3, 2.5, 3.3, 3.6 and 4.6ppm, the proton peaks of the nano starch particles are obviously weakened, and the successful grafting of the polymer on the surface of the nano starch particles modified by the initiator and the successful grafting of the monomers on the surface of the nano starch particles are demonstrated. The quaternary ammonium functional group is formed on the QPDMAEMA-StNP proton peak after quaternization, so that the chemical shift of the tertiary amine functional group proton peak in the PDMAEMA-StNP is increased from 2.5ppm to 3.3ppm, the peak is remarkably broadened, and the success of quaternization modification is proved.

5. Transmission Electron Microscope (TEM)

FIG. 7 shows TEM analysis of corn starch treated with 3.16mol/L sulfuric acid. Analysis shows that the corn starch has a relatively uniform particle size distribution after being treated with sulfuric acid, and the average particle size of the corn starch is about 10-15 nm. This demonstrates that acid catalyzed hydrolysis can produce highly dispersed nano-starches.

FIG. 8 shows TEM analysis of initiator-modified nano-starch particles (StNP-I). Analysis shows that after the surface modification, the particle size distribution of the nano starch particles is more concentrated and relatively uniform, and the average particle size is about 12-20 nm. The particle size is reduced, which is the reason that hydrogen bonds among nano starch particle molecules are weakened after a small molecular initiator is introduced, the dispersibility is improved, and the agglomeration of nano starch particles is further reduced.

FIGS. 9 and 10 show TEM analyses of the starch surface graft polymer (PDMAEMA-StNP) and the quaternized starch surface graft polymer (QPDMAEMA-StNP). Analysis can find that the particle size of the nano starch particle modified by PDMAEMA is remarkably increased by one time to 20-30nm, the particle size distribution is wide, and compared with the TEM analysis result in the foregoing, the particle size of the nano starch particle subjected to surface graft copolymerization is remarkably increased and is a result of polymer modification. The particle size of the nano starch particles after quaternization is further increased to 110-130nm, which causes the agglomeration of the starch surface graft polymer nano particles in the quaternization process.

TEM analysis results show that the hydrolysis time has great influence on the particle size distribution of the nano starch particles when the starch acid is used for catalyzing and hydrolyzing to prepare the nano starch particles; the initiator modified nano starch particles have uniform particle size distribution and small particle size. The PDMAEMA modified nano-starch particles have the advantages that the particle size is remarkably increased due to the coating effect of the macromolecular polymer, and the particle size is further increased due to quaternization. But before and after the surface modification treatment, the surface appearance of the nano starch is not obviously changed, and a more regular spherical structure is basically kept.

Performance test of quaternary ammonium polymer modified nano starch composite material

1. Sensitivity to temperature and pH

DMAEMA is a polymer that is temperature and pH sensitive. The molecular structure unit of the compound has hydrophilic tertiary amino, carbonyl and hydrophobic alkyl groups, and the two groups are matched with each other in space structure. The sensitivity of the starch surface graft polymer before and after quaternization to temperature and pH value is examined.

FIG. 11 shows the effect of pH on the dispersibility of PDMAEM-StNP. The pH of (a) is 4.0, and the pH of (b) is 10.0 at a concentration of 2mg/mL, and analysis shows that the dispersity of the PDMAEM-StNP is reduced along with the increase of the pH, which indicates that the nano starch modified by surface graft copolymerization has better pH sensitivity.

FIG. 12 shows the effect of pH on QPDMAEMA-StNP absorbance. Through analysis, the absorbance of QPDMAEMA-StNP is slightly increased along with the increase of pH in the pH range of 4-8, which indicates that the pH sensitivity of the nano starch after surface graft copolymerization modification is lower. However, when the pH value is increased from 8 to 12, the absorbance is obviously increased, which shows that the nano starch modified by surface graft copolymerization has better pH sensitivity performance in a higher pH value range.

Fig. 13 shows the effect of temperature on the swelling capacity of PDMAEM-StNP in a buffer solution at pH 9.18. Analysis shows that the swelling degree of PDMAEM-StNP is gradually reduced along with the increase of temperature, which indicates that the nano starch modified by surface graft copolymerization has better temperature sensitivity.

FIG. 14 comparison of dispersibility in dichloromethane before and after nano-starch modification (30 min). (a) StNP, (b) StNP-I, (c) PDMAEMA-StNP, and (d) QPDMAEMA-StNP. Analysis shows that the nanometer starch has low dispersity in methylene dichloride and local precipitation. The dispersing performance of the initiator modified nano starch (StNP-I) in dichloromethane is not changed greatly, the dispersibility of the nano starch surface graft polymer (PDMAEM-StNP) and the quaternized surface graft polymer (QPDMAEMA-StNP) in dichloromethane is improved remarkably, no precipitate appears, and the starch modified by surface graft copolymerization can be uniformly dispersed in a solvent with smaller polarity. The dispersibility of the nano starch in a non-polar solvent is low, the particle size of nano starch particles modified by the initiator is small, a certain nano effect is shown, the dispersibility is improved to a certain extent, and the surface of the nano starch modified by the polymer is coated by the polymer with amphipathy, so that the amphipathy is shown to a certain extent.

2. Adsorption Property

FIG. 15 is a graph showing the equilibrium adsorption amount of the graft-modified starch to a potassium chromate solution as a function of concentration. Through comparison, the equilibrium adsorption capacity of PDMAEMA-StNP on chromate in the solution is rapidly increased along with the increase of the concentration when the concentration is lower, and the equilibrium adsorption capacity of the PDMAEMA-StNP tends to be flat along with the change of the concentration when the concentration of potassium chromate continues to increase, and the maximum equilibrium adsorption capacity of the PDMAEMA-StNP is about 260 mg/g. The equilibrium adsorption capacity of the QPDMAEMA-StNP sample subjected to quaternization modification is almost linearly increased along with the increase of the concentration in an experimental concentration range, when the concentration of potassium chromate is lower than 3000mg/L, the equilibrium adsorption capacity is lower than that of PDMAEMA-StNP, and when the concentration of potassium chromate is higher than that, the equilibrium adsorption capacity is higher than that of PDMAEMA-StNP. The reason for this is due to the difference in adsorption mechanism between the two. For the PDMAEMA-StNP sample, the adsorption effect mainly depends on the space effect of the polymer grafted on the surface of starch, the hydrophilic performance of the QPDMAEMA-StNP polyelectrolyte sample after quaternization modification is greatly improved, the polymer chain has a certain degree of ion exchange capacity, when the concentration of potassium chromate is lower, the ion exchange capacity is lower, the adsorption effect on chromate in the solution is mainly realized, and the simple physical adsorption capacity is smaller than that of the polymer which is not subjected to quaternization treatment, so that when the concentration of chromate is continuously increased, the ion exchange capacity is increased, and the equilibrium adsorption capacity is even higher than that of the PDMAEMA-StNP.

The adsorption experiment result of the grafted and modified nano starch on chromate shows that the surface physicochemical property of the nano starch is obviously improved after the surface grafting modification of the nano starch, and the nano starch has a better effect on removing heavy metals in toxic wastewater. The nano starch grafted and modified at a lower concentration has larger equilibrium adsorption capacity, the adsorption capacity is higher than that of a PDMAEMA gel material reported in the literature, and the QPDMAEMA-StNP has larger equilibrium adsorption capacity at a higher concentration, so that the polymer modified nano starch composite material has better application prospect in the aspect of treating wastewater containing toxic heavy metal ions.

The adsorption of the starch after grafting modification to chromate is reversible, and in order to search a regeneration method of a sample after adsorption equilibrium, acid-base soaking treatment, electrolyte solution exchange and a method for changing the polarity of the solution are tried in the experimental process, but only one method is found to be difficult to achieve. Repeated exploration shows that the sample after adsorption balance is soaked for a plurality of minutes by 0.1mol/L hydrochloric acid, and then is soaked in acetone after centrifugal separation, so that the regeneration of the sample after adsorption experiment can be rapidly realized. The adsorption capacity of the regenerated sample can be restored to the original level. The acetone and the potassium chromate are easy to be completely separated, so that the metal ions in the simulated wastewater are completely separated. The reason is that the sample after grafting modification has better dispersibility in an acid solution, which is beneficial to the desorption of the adsorbed sample.

The invention takes corn starch as raw material, and prepares highly dispersed nano starch through acid catalytic hydrolysis; then 2-bromine isobutyryl bromide is used as an initiator, triethylamine is used as an acid-binding agent, and the initiator modified nano starch is prepared; then, taking 2-bromoisobutyryl bromide modified nano-starch particles as an initiator, and carrying out polymerization modification on DMAEMA to obtain a PDMAEMA modified nano-starch particle composite material PDMAEMA-StNP; and finally, carrying out quaternization modification to obtain a target product QPDMAEMA-StNP, wherein the product has good dispersibility, pH value and temperature responsiveness. XRD, XPS, NMR and TEM characterization results show that the nano starch graft polymer is based on surface initiation, and the prepared nano starch composite material is of a core-shell structure coated by the nano starch surface polymer; the structure and the surface appearance of the nano starch polymer after further quaternization modification are not obviously changed.

The invention has the beneficial effects that: the product has good dispersibility, pH value and temperature responsiveness. XRD, XPS, NMR and TEM characterization results show that the nano starch graft polymer is based on surface initiation, and the prepared nano starch composite material is of a core-shell structure coated by the nano starch surface polymer; the structure and the surface appearance of the further quaternized modified nano starch polymer are not obviously changed; the quaternary ammonium polymer modified nano-starch composite material prepared by the invention has good adsorption performance on chromate in simulated sewage, and has good application prospect in environmental management; and the application of the polymer modified nano-starch in the fields of drug controlled release, the bactericidal performance of quaternary ammonium type polyelectrolyte and the like can be continuously explored by utilizing the good pH value and temperature responsiveness of the modified nano-starch composite material, so that the application field of the nano-starch is expanded.

Drawings

FIG. 1 is an infrared spectrum of a starch surface graft polymer and a raw material;

FIG. 2 is a diagram showing the results of XRD analysis of a starch surface graft polymer and a raw material;

FIG. 3 is a graph showing the change in surface composition of the starch surface graft polymer and the raw material;

FIG. 4 is a graph showing the results of C1s spectrum peak splitting of product samples at different stages in the process of nano starch graft modification;

FIG. 5 comparison of XPS analysis results of N1s element on the surface of starch surface graft polymer;

FIG. 6 is a graph showing the results of 1H NMR analyses of StNP (a), StNP-I (b), PDMAEMA-StNP (c), and QPDMAEMA-StNP (d);

FIG. 7 is a graph of TEM analysis results after hydrolysis by 11 d;

FIG. 8 is a TEM analysis result of StNP-I;

FIG. 9 is a TEM analysis result chart of PDMAEMA-StNP;

FIG. 10 is a graph showing the results of TEM analysis of QPDMAEMA-StNP;

FIG. 11 is a graph showing the effect of different pH values on the dispersibility of PDMAEMA-StNP;

FIG. 12 is a graph showing the effect of different pH values on QPDMAEMA-StNP absorbance;

FIG. 13 is a graph showing the effect of temperature on the degree of swelling of PDMAEMA-StNP; .

FIG. 14 is a graph comparing the dispersibility in methylene chloride before and after nano-starch modification;

FIG. 15 is a graph showing the equilibrium adsorption amount of graft-modified starch as a function of concentration.

In the figure: StNP-nano starch particles; StNP-I-2-bromo isobutyryl bromide modified nano-starch particles; PDMAEMA-StNP-PDMAEMA modified nano-starch particle; QPDMAEMA-StNP-quaternized polymer modified nano-starch granular material.

Detailed Description

The preparation and properties of the quaternized polymer modified nano-starch particulate materials of the present invention are further illustrated by the examples below.

Example 1

(1) Preparation of nano-starch granules

Accurately measuring 200mL of 3.16mol/L dilute sulfuric acid in a 250mL three-neck flask; weighing 40.64g of vacuum-dried raw corn starch, adding the raw corn starch into a three-neck flask, respectively hydrolyzing in an oil bath at 30 ℃ for 8 days, then centrifuging at 10000rpm at a high speed, freeze-drying for 20h, and then vacuum-drying at 60 ℃ for 20h to obtain nano starch particles (StNP). TEM analysis shows that after 11 days, the starch has relatively uniform particle size distribution, the average particle size is about 10nm, and the yield is 20%.

(2) Preparation of 2-bromoisobutyryl bromide modified nano starch particles

Adding 80mg of the prepared nano starch into a 100mL three-neck flask, then adding 20mL of dichloromethane, purging with high-purity nitrogen, replacing air in the flask, sealing with a rubber stopper, opening a magnetic stirrer, and slowly dropwise adding 2.8mL of triethylamine by using the amount of an injector; after 10min, slowly injecting 2.4mL of 2-bromo isobutyryl bromide through a rubber plug by using an injector, carrying out surface modification polymerization at the room temperature of 25 ℃ for 24h, then carrying out high-speed centrifugation at 10000rpm, then washing with acetone and centrifuging for three times, air-drying in a centrifugal test tube, and carrying out vacuum drying at the temperature of 60 ℃ for 24h to obtain initiator-modified nano starch particles (StNP-I). TEM analysis shows that after surface modification, the nano starch grains have concentrated and relatively homogeneous size distribution and average size of about 12 nm. The particle size is reduced, which is the reason that hydrogen bonds among nano-particle molecules are weakened after a small-molecule initiator is introduced, the dispersibility is improved, and the nano-particle agglomeration is further reduced.

(3) Preparation of PDMAEMA modified nano starch particles

Accurately measuring 30mL of deionized water, adding the deionized water into a test tube with a support, sealing the test tube with a rubber stopper, purging and replacing air by high-purity nitrogen, adjusting the water temperature to the experimental temperature, transferring 4mL of DMAEMA (dimethylaminoethyl methacrylate) by using an injector, slowly injecting the DMAEMA into the test tube with the support, and then respectively adding 90mg of 2,2 '-bipyridyl and cuprous bromide (the molar ratio of the 2, 2' -bipyridyl to the cuprous bromide is 1: 2); blowing by using high-purity nitrogen after the reagent is added each time, adding 80mg of initiator modified nano starch particles (StNP-I) after the solid reagent is completely dissolved to form a uniform brown solution, reacting until the solution becomes a uniform blue transparent solution, centrifuging at a high speed at 10000rpm, separating the polymerization product, repeatedly washing by using acetone and centrifuging to remove the polymerization product until the polymerization product is white or colorless and transparent. Air-drying the polymerization product at room temperature, and then carrying out vacuum drying at the temperature of 60 ℃ for 20h to obtain a surface graft copolymerized PDMAEMA modified nano starch product (PDMAEMA-StNP). TEM analysis results show that the particle size of the PDMAEMA modified nano starch is remarkably increased by one time to 20nm, the particle size distribution is wide, and compared with the TEM analysis results, the particle size of the nano starch subjected to surface graft copolymerization is remarkably increased and is a polymer modification result.

(4) Preparation of quaternary ammonium polymer modified nano starch granular material

Accurately measuring 5mL of nitromethane, adding the nitromethane into a test tube with a support, introducing high-purity nitrogen to purge and replace air in the test tube, adding 1mL of iodomethane, uniformly mixing, adding a 20mg PDMAEMA-StNP sample, reacting for 20h in a dark place under the conditions of room temperature and nitrogen protection, after the reaction is finished, centrifuging at a high speed of 10000rpm, washing a separation product with acetone, centrifuging for three times, air-drying at room temperature, and drying for 20h in vacuum at the temperature of 60 ℃ to obtain the quaternary ammonium polymer modified nano starch particles (QPDMAEMA-StNP). TEM analysis shows that the particle size of the quaternized nano starch particles (QPDMAEMA-StNP) is further increased to 110nm, which causes the agglomeration of starch surface graft polymer nanoparticles in the quaternization process.

The adsorption test shows that the maximum equilibrium adsorption quantity of QPDMAEMA-StNP on chromate is about 320 mg/g.

Example 2

(1) Preparation of nano-starch granules

Accurately measuring 100mL of 3.16mol/L dilute sulfuric acid in a 250mL three-neck flask; weighing 20.32g of vacuum-dried raw corn starch, adding the raw corn starch into a three-neck flask, respectively hydrolyzing for 10 days in 35 ℃ oil bath, then centrifuging at 11000rpm at a high speed, freeze-drying for 22h, and then vacuum-drying for 22h at 70 ℃ to obtain nano starch particles (StNP). TEM analysis shows that after 11 days, the starch has relatively uniform particle size distribution, the average particle size is about 12nm, and the yield is 25%.

(2) Preparation of 2-bromoisobutyryl bromide modified nano starch particles

And (3) adding 40mg of the prepared nano starch into a 100mL three-neck flask, then adding 10mL of dichloromethane, purging with high-purity nitrogen, replacing air in the flask, sealing with a rubber stopper, and opening a magnetic stirrer. 1.4mL of triethylamine was slowly added dropwise with the amount of a syringe. After 10min, slowly injecting 1.2mL of 2-bromo isobutyryl bromide through a rubber plug by using an injector, carrying out surface modification polymerization at room temperature of 25 ℃ for 24h, then carrying out high-speed centrifugation at 11000rpm, then washing with acetone and centrifuging for three times, air-drying in a centrifugal test tube, and carrying out vacuum drying at 65 ℃ for 22h to obtain initiator-modified nano starch particles (StNP-I). TEM analysis shows that after surface modification, the nano starch grains have concentrated and relatively uniform grain size distribution and average grain size of about 15 nm. The particle size is reduced, which may be the reason that the hydrogen bonds between the nano-particle molecules are weakened after the small-molecule initiator is introduced, the dispersibility is improved, and the nano-particle agglomeration is further reduced.

(3) Preparation of PDMAEMA modified nano starch particles

Accurately measuring 15mL of deionized water, adding the deionized water into a test tube with a support, sealing the test tube with a rubber plug, purging and replacing air by high-purity nitrogen, adjusting the water temperature to the experimental temperature, transferring 2mL of DMAEMA (dimethylaminoethyl methacrylate) by using an injector, slowly injecting the DMAEMA into the test tube with the support, and then respectively adding 45mg of 2, 2' -bipyridine and cuprous bromide according to a molar ratio of 1: 2. After the reagent is added, high-purity nitrogen is used for blowing, and after the solid reagent is completely dissolved to form a uniform brown solution, 40mg of initiator modified nano starch (StNP-I) is added. After the reaction until the solution became a uniform blue transparent solution, it was centrifuged at a high speed of 12000rpm, and the polymer product was separated, washed repeatedly with acetone and centrifuged to remove the polymer product until it became white or colorless transparent. Air-drying the polymerization product at room temperature, and then carrying out vacuum drying at the temperature of 60 ℃ for 24h to obtain a surface graft copolymerized PDMAEMA modified nano starch product (PDMAEMA-StNP). TEM analysis results show that the particle size of the PDMAEMA modified nano starch is remarkably increased by about one time to 25nm, the particle size distribution is wide, and compared with the TEM analysis results, the particle size of the nano starch subjected to surface graft copolymerization is remarkably increased, and the nano starch is probably a polymer modification result.

Accurately measuring 2.5mL of nitromethane, adding the nitromethane into a test tube with a support, introducing high-purity nitrogen to purge and replace air in the test tube, adding 0.5mL of iodomethane, uniformly mixing, adding 10mg of PDMAEMA-StNP sample, and reacting for 24 hours in a dark place at room temperature under the protection of nitrogen. And after the reaction is finished, centrifuging at a high speed of 12000rpm, washing a separation product by using acetone, centrifuging for three times, air-drying at room temperature, and then drying in vacuum at 65 ℃ for 22 hours to obtain the quaternary ammonium polymer modified nano starch particles (QPDMAEMA-StNP). TEM analysis shows that the particle size of quaternized nano starch particles (QPDMAEMA-StNP) is further increased to 120nm, which may cause agglomeration of starch surface graft polymer nanoparticles in the quaternization process.

The adsorption test shows that the maximum equilibrium adsorption quantity of QPDMAEMA-StNP on chromate is about 340 mg/g.

Example 3

(1) Preparation of nano-starch granules

Accurately measuring 250mL of 3.16mol/L dilute sulfuric acid in a 500mL three-neck flask; weighing 50.8g of vacuum-dried raw corn starch, adding into a three-neck flask, hydrolyzing in oil bath at 40 ℃ for 11 days respectively, then centrifuging at 12000rpm at a high speed, freeze-drying for 24h, and then vacuum-drying at 70 ℃ for 24h to obtain nano starch particles (StNP). TEM analysis shows that after 11 days, the starch has relatively uniform particle size distribution, the average particle size is about 15nm, and the yield is 26%.

(2) Preparation of 2-bromoisobutyryl bromide modified nano starch particles

And (3) adding 100mg of the prepared nano starch into a 250mL three-neck flask, then adding 25mL dichloromethane, purging with high-purity nitrogen, replacing air in the flask, sealing with a rubber stopper, and opening a magnetic stirrer. 3.5mL of triethylamine was slowly added dropwise with the amount of a syringe. After 10min, 3.0mL of 2-bromo isobutyryl bromide is slowly injected through a rubber stopper by using a syringe, surface modification polymerization is carried out at room temperature of 25 ℃ for 24h, then high-speed centrifugation is carried out at 12000rpm, then washing and centrifugation are carried out for three times by using acetone, air drying is carried out in a centrifugal test tube, and vacuum drying is carried out at 70 ℃ for 24h, so as to obtain initiator modified nano starch particles (StNP-I). TEM analysis shows that after surface modification, the nano starch grains have concentrated and relatively homogeneous size distribution and average size of about 20 nm. The particle size is reduced, which may be the reason that the hydrogen bonds between the nano-particle molecules are weakened after the small-molecule initiator is introduced, the dispersibility is improved, and the nano-particle agglomeration is further reduced.

(3) Preparation of PDMAEMA modified nano starch particles

Accurately measuring 37.5mL of deionized water, adding the deionized water into a test tube with a support, sealing the test tube with a rubber stopper, purging and replacing air by high-purity nitrogen, adjusting the water temperature to the experimental temperature, using an injector to remove 5.0mL of DMAEMA (dimethylaminoethyl methacrylate) and slowly injecting the DMAEMA into the test tube with the support, and then respectively adding 112.5mg (the molar ratio of 2, 2' -bipyridine to cuprous bromide is 1: 2). After the reagent is added, high-purity nitrogen is used for blowing, and after the solid reagent is completely dissolved to form a uniform brown solution, 100mg of initiator modified nano starch particles (StNP-I) are added. After the reaction until the solution became a uniform blue transparent solution, it was centrifuged at a high speed of 12000rpm, and the polymer product was separated, washed repeatedly with acetone and centrifuged to remove the polymer product until it became white or colorless transparent. And (3) air-drying the polymerization product at room temperature, and then carrying out vacuum drying at the temperature of 70 ℃ for 24h to obtain a surface graft copolymerized PDMAEMA modified nano starch product (PDMAEMA-StNP). TEM analysis results show that the particle size of the PDMAEMA modified nano starch is remarkably increased by one time to 30nm, the particle size distribution is wide, and compared with the TEM analysis results, the particle size of the nano starch subjected to surface graft copolymerization is remarkably increased and is a polymer modification result.

Accurately measuring 6.25mL of nitromethane, adding the nitromethane into a test tube with a support, introducing high-purity nitrogen to purge and replace air in the test tube, adding 1.25mL of iodomethane, uniformly mixing, adding 25mg of PDMAEMA-StNP sample, and reacting for 24 hours in a dark place at room temperature under the protection of nitrogen. And after the reaction is finished, centrifuging at a high speed of 12000rpm, washing a separation product by using acetone, centrifuging for three times, air-drying at room temperature, and then drying in vacuum at 70 ℃ for 24 hours to obtain the quaternary ammonium polymer modified nano starch particle (QPDMAEMA-StNP). TEM analysis shows that the particle size of quaternized nano starch particles (QPDMAEMA-StNP) is further increased to 130nm, which may cause agglomeration of starch surface graft polymer nanoparticles in the quaternization process.

Adsorption experiments show that the maximum equilibrium adsorption capacity of QPDMAEMA-StNP on chromate is about 350 mg/g.

The present invention is not limited to the above-mentioned preferred embodiments, and any other products in various forms can be obtained by anyone in the light of the present invention, but any changes in the shape or structure thereof, which have the same or similar technical solutions as those of the present application, fall within the protection scope of the present invention.

Claims

1. A preparation method of a quaternary ammonium polymer modified nano starch particle composite material is characterized by comprising the following steps:

step (1), preparation of nano starch particles: dispersing the corn starch after vacuum drying in 2-4 mol/L dilute sulfuric acid, hydrolyzing in an oil bath at 30-40 ℃ for 8-11 days, centrifuging at high speed, and drying to obtain nano starch particles;

step (2) preparation of 2-bromoisobutyryl bromide modified nano-starch particles: using dichloromethane as a solvent, triethylamine as an acid-binding agent and 2-bromoisobutyryl bromide as an initiator, modifying the nano-starch particles prepared in the step (1) at room temperature for 20-24 hours under the protection of nitrogen and stirring, centrifuging at a high speed, separating a product, washing with acetone, and drying to obtain 2-bromoisobutyryl bromide modified nano-starch particles;

step (3) preparation of PDMAEMA modified nano-starch particles: using deionized water as a solvent, using the 2-bromoisobutyryl bromide modified nano-starch particles prepared in the step (2) as an initiator, using 2, 2' -bipyridine and cuprous bromide as a composite catalyst, and modifying dimethylaminoethyl methacrylate at 30-40 ℃ under the protection of nitrogen and stirring; after the reaction solution becomes uniform blue transparent solution, centrifuging at high speed, washing the separated product with acetone, and drying to obtain PDMAEMA modified nano-starch particles;

step (4), preparation of the quaternary ammonium polymer modified nano starch granular material: reacting the PDMAEMA modified nano-starch particles prepared in the step (3) at room temperature in a dark place for 20-24 hours by using nitromethane as a solvent and iodomethane as a quaternizing agent under the protection of nitrogen; and after the reaction is finished, centrifuging at a high speed, washing a separation product by using acetone, and drying to obtain the quaternary ammonium polymer modified nano starch particle composite material.

2. The method of making a quaternized polymer-modified nano-starch particle composite of claim 1, wherein: the drying in the step (1) comprises the following steps: freeze drying for 20-24 hr, and vacuum drying at 60-70 deg.C for 20-24 hr.

3. The method of making a quaternized polymer-modified nano-starch particle composite of claim 1, wherein: in the step (2), the dosage of triethylamine is 0.02-0.03 time of the mass of the nano starch particles; the dosage of the initiator 2-bromo isobutyryl bromide is 0.05-0.06 time of the mass of the nano starch particles.

4. The method of making a quaternized polymer-modified nano-starch particle composite of claim 1, wherein: in the step (3), the dosage of the monomer dimethylaminoethyl methacrylate is 0.1-0.3 times of the mass of the 2-bromoisobutyryl bromide modified nano starch particles.

5. The method of making a quaternized polymer-modified nano-starch particle composite of claim 1, wherein: in the composite catalyst in the step (3), the molar ratio of 2, 2' -bipyridyl to cuprous bromide is 1: 1-3; the dosage of the composite catalyst is 0.05 to 0.06 time of the molar weight of the monomer dimethylaminoethyl methacrylate.

6. The method of making a quaternized polymer-modified nano-starch particle composite of claim 1, wherein: in the step (4), the molar ratio of the methyl iodide to the N, N-dimethylaminoethyl methacrylate modified nano-starch particles is 1: 3.0-3.5.

7. the method of making a quaternized polymer-modified nano-starch particle composite of claim 1, wherein: in the step (4), the dosage of the nitromethane is 10-15 times of the molar weight of the iodomethane.

8. The method of making a quaternized polymer-modified nano-starch particle composite of claim 1, wherein: the drying in the steps (2), (3) and (4) is vacuum drying at 60-70 ℃ for 20-24 hours.

9. The method of making a quaternized polymer-modified nano-starch particle composite of claim 1, wherein: the high-speed centrifugation speed in each step is 10000-12000 r/min.

10. The use of the quaternized polymer-modified nano starch granule composite material prepared by the preparation method of claim 1 in adsorption treatment of chromate-containing wastewater.