Polymer microspheres, method for manufacturing polymer microspheres, and polymer film comprising polymer microspheres

Abstract

Provided are polymer microspheres, a method for manufacturing polymer microspheres, and a polymer film comprising polymer microspheres. The polymer microspheres contain a cardanol moiety. The method for manufacturing polymer microspheres comprises the steps of: supplying a first monomer containing a cardanol moiety to a solvent; and suspension-polymerizing the first monomer. The polymer film comprises the polymer microspheres.

Description

Polymer microspheres, method for producing polymer microspheres, and polymer film comprising polymer microspheres

[0001] The present invention relates to polymer microspheres, a method for producing polymer microspheres, and a polymer film comprising polymer microspheres.

[0002] Since the advent of antimicrobials, the average human life expectancy and lifespan have increased dramatically, making it possible to effectively control bacterial and microbial infections. However, the continued use of antimicrobials has led to the emergence of resistant bacteria. Over the past several decades, research has focused on developing antimicrobials that do not develop resistance. Existing single-molecule antimicrobials exhibit antimicrobial activity through mechanisms such as interfering with or inhibiting specific bacterial metabolism. However, these antimicrobials often lead to the development of resistant bacteria. Therefore, antimicrobials that directly destroy bacterial cell walls have been developed. However, these antimicrobials struggle to maintain sustained antimicrobial activity and have low biocompatibility.

[0003] The present invention provides polymer microspheres having antibacterial properties.

[0004] The present invention provides a method for producing polymer microspheres having antibacterial properties.

[0005] The present invention provides a polymer film having antibacterial properties.

[0006] Other objects of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0007] Polymer microspheres according to embodiments of the present invention comprise cardanol moieties.

[0008]

[0009] A method for producing polymer microspheres according to embodiments of the present invention comprises the steps of providing a first monomer comprising a cardanol moiety to a solvent, and the steps of suspension polymerizing the first monomer.

[0010]

[0011] A polymer film according to embodiments of the present invention includes the polymer microspheres.

[0012] Polymer microspheres according to embodiments of the present invention can have excellent antibacterial properties and biocompatibility. The polymer microspheres can be utilized as various antibacterial coating materials, and polymer films having excellent antibacterial properties and biocompatibility can be realized using the polymer microspheres.

[0013] FIG. 1 is a drawing for explaining a method for manufacturing polymer microspheres according to one embodiment of the present invention.

[0014] Figure 2 shows the DSC heating curves of mPCM and PCM.

[0015] Figure 3 shows the FT-IR / ATR spectra of mPCM and PCM in the high-frequency region.

[0016] Figure 4 shows the FT-IR / ATR spectra of mPST, mPCM, and mPCMST-x.

[0017] Figure 5 shows the DSC heating curves of mPST, mPCM, and mPCMST-x.

[0018] Figure 6 shows the TGA curves of mPST, mPCM, and mPCMST-x.

[0019] Figure 7 shows the antibacterial properties of a polymer film manufactured with mPCMST-x.

[0020] Figure 8 shows the antibacterial properties of a polymer film manufactured with PCMST-x.

[0021] Hereinafter, the present invention will be described in detail through examples. The objectives, features, and advantages of the present invention will be readily understood through the following examples. The present invention is not limited to the examples described herein and may be embodied in other forms. The examples introduced herein are provided to ensure that the disclosure is thorough and complete and to sufficiently convey the spirit of the present invention to those skilled in the art. Therefore, the present invention should not be limited by the following examples.

[0022]

[0023] Polymer microspheres according to embodiments of the present invention comprise cardanol moieties.

[0024] The above polymer microspheres can be prepared by suspension polymerizing a first monomer comprising the cardanol moiety.

[0025] The above first monomer may have the following chemical formula 1.

[0026] [Chemical Formula 1]

[0027]

[0028] The above cardanol moiety may include an unsaturated hydrocarbon, and the unsaturated hydrocarbon may react during the suspension polymerization to form a crosslinked structure.

[0029] In the above suspension polymerization, a second monomer may be copolymerized with the first monomer, and the second monomer may include styrene.

[0030]

[0031] A method for producing polymer microspheres according to embodiments of the present invention comprises the steps of providing a first monomer comprising a cardanol moiety to a solvent, and the steps of suspension polymerizing the first monomer.

[0032] The above first monomer may have the following chemical formula 1.

[0033] [Chemical Formula 1]

[0034]

[0035] The above cardanol moiety may include an unsaturated hydrocarbon, and the unsaturated hydrocarbon may react during the suspension polymerization to form a crosslinked structure.

[0036] The above first monomer can be dissolved in methylene chloride together with an initiator and then provided to the solvent.

[0037] The solvent may include water and a stabilizer, and the initiator may include AIBN.

[0038] The first monomer may be provided to the solvent together with a second monomer, and the second monomer may include styrene.

[0039]

[0040] A polymer film according to embodiments of the present invention includes the polymer microspheres.

[0041]

[0042] [Manufacture of polymer microspheres and polymer films]

[0043]

[0044] Polymer microspheres can be prepared using suspension polymerization. For preparing polymer microspheres, 1 g of the monomer (CM (2-hydroxy-3-cardanylpropyl methacrylate) or a mixture of CM and styrene) and 50 mg of AIBN (azobisisobutyronitrile) are dissolved in 2 mL of methylene chloride and then added to 50 mL of an aqueous solution containing 1 wt% sodium dodecyl sulfate (SDS). The reaction mixture is degassed and stirred for 30 minutes under a N2 atmosphere. Suspension polymerization is performed under N2 atmosphere at 70°C for 18 hours with stirring at 300 rpm. After polymerization, the polymer microspheres are centrifuged to remove the surfactant and initiator. The supernatant is removed and the precipitate is washed with deionized water. An aliquot of the reaction mixture is used to determine the initial concentration and monomer conversion. Monomer conversion is measured using the freeze-drying method based on the weight of polymer contained in the mixture.

[0045] A polymer film containing polymer microspheres is prepared by dropping 0.3 mL of a 3 wt% aqueous solution of polymer microspheres onto a glass substrate and then drying it in the air overnight.

[0046]

[0047] Polymers containing CM and / or styrene are prepared by solution polymerization to compare their antibacterial activity with polymer microspheres. 1 g of monomer (CM, styrene, or a mixture of CM and styrene) and 50 mg of AIBN are dissolved in 5 mL of tetrahydrofuran (THF). The reaction mixture is solution polymerized at 70°C for 18 h under a N2 atmosphere with stirring at 300 rpm. After polymerization, the reaction product is cooled to room temperature and added to an excess of deionized water and methanol (6:1) with stirring to precipitate the synthesized polymer. The product is dissolved in tetrahydrofuran (THF) and then vacuum-dried. The polymer is obtained in bulk with a yield of 60–80%.

[0048] Polymer films were prepared by dropping 0.3 mL of a 3 wt% THF solution of the polymer onto a glass substrate and drying it in the air overnight. Crosslinking of the polymer films was performed under a 21,700 mW / cm2 laser beam at a distance of 5 cm for 2 hours in air at room temperature. 2 It is performed by irradiating UV light.

[0049] A PMMA film as a negative control for antibacterial testing was prepared by dropping 0.3 mL of a 3 wt% THF solution of PMMA onto a glass substrate and drying it in the air overnight.

[0050]

[0051] [Measurement of antibacterial activity of polymer microspheres]

[0052]

[0053] To prepare a bacterial suspension, bacteria were cultured, and one of the colonies was placed in 30 ml of nutrient broth solution using a platinum loop and grown at 37°C for 18 hours. After washing with PBS solution, the bacterial solution was diluted in PBS to 10 6CFU (colony forming unit) / ml. The concentration of the bacterial suspension is estimated by measuring the absorbance of the cell dispersion at 600 nm using an ultraviolet-visible spectrometer and referring to a standard calibration curve. The optical density (OD) of 1 at 600 nm is approximately 10 9 It is equal to CFU / ml.

[0054] The Minimum Inhibitory Concentration (MIC) test is performed on the Gram-negative bacterium Escherichia coli ATCC 8739. The bacteria are cultured at 35°C for 24 hours in a medium containing polymeric microspheres distributed in a 96-well plate. The polymeric microspheres are diluted 2-, 4-, 8-, 16-, 32-, and 64-fold in liquid medium. Because the turbidity of the polymer emulsion makes it difficult to detect bacterial growth using a UV-Vis spectrometer, 10 μl of the culture medium is diluted 100-fold with water, and 100 μl of the diluted suspension is inoculated onto agar growth medium. The MIC is given as the lowest polymeric microsphere concentration at which no colonies are detected.

[0055]

[0056] [Measurement of antibacterial activity of polymer films]

[0057]

[0058] To evaluate the antibacterial properties of the polymer film, 0.1 mL of bacterial suspension is dropped onto the surface of the polymer film placed in a petri dish, and the polymer film is covered with an OHP film of the same size as the polymer film so that the bacterial solution is in complete contact with the polymer film at 25°C. After 24 hours, the OHP film is removed, and 0.9 mL of PBS solution is added to the petri dish containing the sample. The petri dish is shaken vigorously so that the bacteria present on the substrate are detached from the surface of the polymer film and transferred to a microtube. The bacterial solution is diluted, and 0.1 mL of the diluent is spread on the agar medium. The number of remaining colonies is counted after 18 hours at 37°C, and each analysis is repeated three times. The bacterial inhibition rate is calculated using the following equation.

[0059] Bacterial inhibition rate (%) = 100 × (N o -N i ) / N o

[0060] In the above formula, N o is the bacterial CFU of the blank, and N i is the bacterial CFU of the tested sample.

[0061] The morphology of microorganisms on polymer films was investigated using SEM analysis. After strain culture, the sample films were fixed (2.5% glutaraldehyde, 120 min) and dehydrated (25, 50, 70, 90, 95, and 100% ethanol solutions). After air-drying, the sample films were coated with platinum and observed using a SEM. The inhibition zone test was performed according to the following procedure. 0.1 mL of an E. coli suspension at a concentration of 106 CFU / mL was inoculated onto an agar plate, and a polymer film with a diameter of 0.8 cm was placed on the plate. The samples were incubated in an incubator at 37°C for 18 h.

[0062]

[0063] FIG. 1 is a drawing for explaining a method for manufacturing polymer microspheres according to one embodiment of the present invention.

[0064] Referring to FIG. 1, polymeric microspheres (mPCMs) containing cardanol moieties can be prepared by suspension polymerization of CM (2-hydroxy-3-cardanylpropyl methacrylate).

[0065] First, to synthesize CM, cardanol (10 g) and potassium hydroxide (1.9 g) are placed in a 250 mL round-bottom flask with dimethylacetamide (DMAc, 30 mL) and a stirring bar magnet under a nitrogen atmosphere. Glycidyl methacrylate (9.4 g) is added to the flask and reacted at 60°C for 72 hours. A few drops of hydrochloric acid are added to terminate the reaction and dimethylacetamide is evaporated. After dissolving the product in methylene chloride, a 0.5 N hydrochloric acid solution is added to protonate the salt product, and the methylene chloride layer is extracted and filtered to obtain CM. CM is purified by silica gel column chromatography using a solvent of ethyl acetate and n-hexane in a volume ratio of 1:6.

[0066] In the suspension polymerization of CM, AIBN and SDS (sodium dodecyl sulfate) are used as an initiator and stabilizer, respectively. 50 mL of distilled water and SDS (1 wt%) are placed in a 250 mL round bottom flask with a stirring magnet. 1 g of CM and 50 mg of AIBN are dissolved in 2 mL of methylene chloride and then added to the flask. The reactants are stirred for 30 minutes in a nitrogen atmosphere and then reacted at 300 rpm and 70°C for 18 hours. During the suspension polymerization of CM, the unsaturated hydrocarbons of the cardanol moiety react to form a crosslinked structure. The resulting polymer emulsion is separated and purified using a centrifuge and distilled water. Freeze-drying the separated and purified product yields polymer microspheres (mPCM).

[0067] Because the CM monomer is waxy at room temperature, it is difficult to produce polymer microspheres with a narrow particle size distribution using CM as the sole monomer during suspension polymerization. To overcome this problem, a small amount of methylene chloride is used to separate the monomer liquid crystals during polymerization. Polymer microspheres (mPCMs) produced from CM have a size of 400 to 600 nm and a smooth surface.

[0068] Polymer particles with a size of less than 1 μm are not desirable for antibacterial applications due to issues such as surface area and filtration. When the stirring speed is less than 300 rpm, uniform polymer microspheres cannot be obtained through suspension polymerization. However, when the stirring speed is greater than 300 rpm, smaller polymer microspheres with a narrow size distribution can be obtained. Increasing the stirring speed from 300 rpm to 700 rpm reduces the size of the monomer droplets dispersed in suspension polymerization, resulting in the formation of smaller microspheres. However, when a mixture of CM and styrene is used in suspension polymerization, it is difficult to obtain uniform polymer microspheres when the stirring speed exceeds 300 rpm due to the difference in viscosity between CM and styrene. To eliminate the influence of polydispersity on particle size, a stirring speed of 300 rpm was used to prepare polymer microspheres in the examples of the present invention.

[0069] In addition, copolymer polymer microspheres (mPCMST) can be manufactured by copolymerizing CM and styrene (ST). Copolymer polymer microspheres (mPCMST) can be manufactured in the same manner as polymer microspheres (mPCM) except that styrene is added together with CM to the reactants. Copolymer polymer microspheres can be manufactured by controlling the content of CM, and in mPCMST-x, x represents the mol% of CM contained in the monomers (CM and styrene) supplied to the polymerization reaction. Through copolymerization with styrene, the glass transition temperature and physical properties of copolymer polymer microspheres can be improved, and copolymer polymer microspheres capable of crosslinking can be synthesized through the unsaturated double bonds present in cardanol.

[0070] The synthesis conditions, yield, sphere size, and glass transition temperature of polymer microspheres are shown in Table 1.

[0071] [Table 1]

[0072]

[0073] In Table 1 above, D v (volume-averaged diameter) and C v (coefficient of variation) was determined using DLS.

[0074]

[0075] Figure 2 shows the DSC (differential scanning calorimeter) heating curves of mPCM and PCM, and Figure 3 shows the FT-IR / ATR spectra of mPCM and PCM in the high-frequency region. PCM represents a polymer prepared by solution polymerization of CM.

[0076] Referring to Fig. 2, the glass transition temperature of mPCM is 32.5℃, which is higher than the glass transition temperature of PCM, which is -13.9℃, and the crosslinking reaction enthalpy change value of mPCM is 20.04 J / g, which is smaller than the crosslinking reaction enthalpy change value of PCM, which is 111.35 J / g. The exothermic peak indicated at approximately 175℃ in the heating curves of PCM and mPCM indicates that a crosslinked structure was formed from the unsaturated hydrocarbon of the cardanol moiety during the heating scan, and mPCM shows a smaller exothermic peak than PCM. Therefore, mPCM prepared by suspension polymerization has a higher crosslinking density than PCM prepared by solution polymerization. Because crosslinking restricts the mobility of polymer chains, mPCM shows a higher glass transition temperature (Tg) value than PCM.

[0077] Referring to Figure 3, from the CH vibration absorption of unsaturated hydrocarbon (from cardanol moiety) at 3010 cm -1 The absorption peak appears very small in the FT-IR spectrum of mPCM, indicating that the peak corresponding to the unsaturated double bond decreases due to crosslinking.

[0078] In suspension polymerization, monomer droplets are dispersed in a water phase, acting as independent microreactors, allowing polymerization to proceed in a small, bulk manner. During the polymerization process, monomers are converted to polymers, and the droplets become viscous, allowing crosslinking reactions to occur simultaneously. Crosslinked polymer microspheres are advantageous for polymer coating applications because they can improve the physical and thermal properties of the coating material. Most vinyl polymer microspheres with a crosslinked structure are manufactured using additional crosslinking agents (such as divinyl benzene (DVB) and glycol dimethacrylate) to introduce crosslinking sites into the polymer structure. However, CM automatically acquires a crosslinked structure during suspension polymerization due to the unsaturated hydrocarbon group in the cardanol moiety.

[0079]

[0080] Figure 4 shows the FT-IR / ATR spectra of mPST, mPCM, and mPCMST-x, Figure 5 shows the DSC heating curves of mPST, mPCM, and mPCMST-x, and Figure 6 shows the TGA curves of mPST, mPCM, and mPCMST-x. Copolymer microspheres (mPCMST-x) were prepared through suspension polymerization of CM and styrene, and styrene was selected as a co-monomer due to its wide applicability and low cost. Copolymer microspheres (mPCMST-x) have a spherical morphology with a narrow size distribution regardless of the ratio of CM to styrene.

[0081] Referring to FIGS. 4 to 6, the FT-IR spectrum of mPCMST-x shows the 1728 cm of the CM moiety. -1 It is shown that the intensity of the characteristic C=O stretching vibration of α,β-unsaturated esters increases with increasing CM content, indicating the incorporation of CM moieties into mPCMST-x.

[0082] The DSC curve of mPCMST-x shows that the Tg value decreases from 91.1°C to 32.5°C as the CM content increases from 0 mol% to 100 mol%, indicating that the long alkyl chain of the cardanol moiety acts as a plasticizer.

[0083] The thermal stability of mPCMST-x was investigated by thermogravimetric analysis (TGA) under N2 atmosphere. The thermal decomposition temperature (T) at 10% weight loss of the copolymer microspheres d,10wt% ) are thermally stable for coating applications above 350°C. Increasing the CM content may increase the decomposition temperature due to the increase in crosslinking density. All PCMST-x prepared by solution polymerization have smaller Tg values ​​than mPCMST-x prepared by suspension polymerization, indicating that the crosslinked structure of mPCMST-x increases the thermal transition temperature.

[0084]

[0085] Table 2 shows the minimum inhibitory concentration (MIC) values ​​of polymer microspheres using E. coli as the test bacteria.

[0086] [Table 2]

[0087]

[0088] In Table 2 above, f CM represents the supply ratio of CM monomer to the total monomer supplied to the polymerization reaction, the initial concentration was measured using the lyophilization method based on the weight of the polymer contained in the mixture, and MIC is given as the lowest polymer microsphere concentration at which no colonies are detected.

[0089] Because the turbidity of the polymer emulsion makes it difficult to calculate bacterial growth using the OD600 value, the MIC value was set as the lowest polymer microsphere concentration at which no colonies were detected. mPCMST-x containing CM content of 10 mol% or more exhibited an MIC value of less than 1 mg / mL, indicating that polymer microspheres with cardanol moieties have a significant inhibitory effect on bacterial growth and proliferation.

[0090] Polymer microspheres with lower Tg values ​​have more mobile polymer chains, which can further enhance antibacterial activity. The flexible alkyl chain of the cardanol moiety increases interaction with the bacterial membrane, so the antibacterial activity of the polymer film may be related to the Tg value, and membrane damage due to interaction with the CM moiety may affect the antibacterial activity of the cardanol moiety.

[0091]

[0092] Figure 7 shows the antibacterial activity of a polymer film (mPCMST-x film) manufactured with mPCMST-x, and Figure 8 shows the antibacterial activity of a polymer film (PCMST-x film) manufactured with PCMST-x. The mPCMST-x film was manufactured on a glass substrate by a drop-casting method, and its antibacterial activity was measured by a film adhesion method using E. coli. A PMMA coating film was manufactured as a negative control because it has been widely used as a coating material with bactericidal and antifouling properties. To compare the bactericidal properties between bulk polymers and polymer microspheres, a bulk copolymer polymer (PCMST-x) was manufactured through solution polymerization, and a PCMST-x film was manufactured by drop-casting onto a glass substrate. Since the bulk copolymer polymer film itself is sticky, it was crosslinked through UV irradiation to create a physically stable surface, and the antibacterial activity was measured.

[0093] Referring to FIGS. 7 and 8, the mPCM film has a high bactericidal property of over 99.9% and can effectively kill bacteria. For the mPCMST-x film, the antibacterial activity decreases as the CM content decreases. mPCMST-20 with a CM content of 20 mol% exhibits a high bactericidal power of over 99.9% against E. coli. The bactericidal property of the PCMST-x film also shows a similar trend in that the proportion of live bacteria decreases as the CM content increases. When comparing mPCMST-x (polymer microspheres) and PCMST-x (bulk copolymer polymer), the antibacterial activity of mPCMST-x is higher. For example, no colonies were detected in the mPCMST-20 film, but colonies were still observed in the PCMST-20 film. The higher antibacterial activity of the mPCMST-x film may result from the higher surface area and smaller Tg value of mPCMST-x compared to PCMST-x. Films manufactured from polymer microspheres have a higher surface area than polymer films obtained by solution polymerization due to their spherical shape. mPCMST-x exhibits higher antibacterial activity due to the greater contact area between bacteria and the polymer film.

[0094]

[0095] Polymers containing cardanol functional groups exhibit excellent biocompatibility and exhibit no cytotoxic behavior. Furthermore, the hydrophobic CM moiety results in greater cell adhesion observed in polymer films. Since the extracellular membrane (ECM) is primarily composed of various proteins, a hydrophobic surface can promote the adhesion of living cells. Polymer coatings containing cardanol moieties exhibit both bactericidal and biocompatible properties, suggesting their potential applications in various fields, including biomedical applications, food packaging, and water purification.

[0096]

[0097] We have discussed specific embodiments of the present invention. Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from its essential characteristics. Therefore, the disclosed embodiments should be considered illustrative rather than restrictive. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

[0098] Polymer microspheres according to embodiments of the present invention can have excellent antibacterial properties and biocompatibility. The polymer microspheres can be utilized as various antibacterial coating materials, and polymer films having excellent antibacterial properties and biocompatibility can be realized using the polymer microspheres.

Claims

1. Polymer microspheres containing a cardanol moiety.

2. In paragraph 1, A polymer microsphere characterized in that the polymer microsphere is prepared by suspension polymerizing a first monomer containing the cardanol moiety.

3. In paragraph 2, A polymer microsphere characterized in that the first monomer has the following chemical formula 1. [Chemical Formula 1] 4. In paragraph 2, The above cardanol moiety comprises an unsaturated hydrocarbon, A polymer microsphere characterized in that the above unsaturated hydrocarbon reacts during the suspension polymerization to form a crosslinked structure.

5. In paragraph 2, In the above suspension polymerization, the second monomer is copolymerized together with the first monomer, Polymer microspheres characterized in that the second monomer comprises styrene.

6. A step of providing a first monomer containing a cardanol moiety to a solvent; and A method for producing polymer microspheres, comprising the step of suspension polymerizing the first monomer.

7. In paragraph 6, A method for producing polymer microspheres, wherein the first monomer has the following chemical formula 1. [Chemical Formula 1] 8. In paragraph 6, The above cardanol moiety comprises an unsaturated hydrocarbon, A method for producing polymer microspheres, characterized in that the unsaturated hydrocarbon reacts during the suspension polymerization to form a crosslinked structure.

9. In paragraph 6, A method for producing polymer microspheres, characterized in that the first monomer is dissolved in methylene chloride together with an initiator and then provided to the solvent.

10. In paragraph 6, The solvent comprises water and a stabilizer, A method for producing polymer microspheres, characterized in that the above initiator comprises AIBN.

11. In paragraph 6, The first monomer is provided to the solvent together with the second monomer, A method for producing polymer microspheres, characterized in that the second monomer comprises styrene.

12. A polymer film comprising polymer microspheres comprising cardanol moieties.

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