EP1165671A1

EP1165671A1 - Polymer surface modification by hydrogen ion assisted reaction

Info

Publication number: EP1165671A1
Application number: EP00958997A
Authority: EP
Inventors: Seok-Keun Koh; Jung Cho
Original assignee: Korea Institute of Science and Technology KIST
Current assignee: Korea Institute of Science and Technology KIST
Priority date: 1999-09-16
Filing date: 2000-09-01
Publication date: 2002-01-02
Also published as: EP1165671A4; KR100345289B1; JP2003509558A; CN1321173A; KR20010027898A; WO2001019903A1

Abstract

A method for modifying a polymer surface is provided. Polymers are surface-modified by hydrogen ion assisted reaction and thereby the layers under the surface are converted to hydrophilic functional groups. Also, the present invention is a new method of generating a new kind of chemical bond on the surface and inner layers by damaging C-H or C-H-O bond on the polymer surface using hydrogen ions, while introducing oxygen, a reactive gas, on the surface.

Description

POLYMER SURFACE MODIFICATION BY HYDROGEN ION ASSISTED REACTION

TECHNICAL FIELD

5 The present invention relates to a method of modifying a polymer surface using a hydrogen ion assisted reaction and, in particular, to a method of modifying a polymer sur ace by appropriately irradiating energized hydrogen particles on the surface, while blowing a reactive gas such as oxygen, nitrogen, hydrogen, or carbon dioxide on the io polymer surface under a vacuum condition

BACKGROUND ART

Many studies for modifying a polymer surface have been conducted The U S Patent No 5,965,629 (which is incorporated its i entirety) discloses that functional groups can be formed on the surface of the polymer by blowing reactive gas or gases on the surface, while irradiating energized argon ion particles In this case, the functional groups are only formed on the surface, and thus it is difficult to form the functional groups below the surface of the polymer material e g , a thin 0 polymer layer of several microns which requires abrasion resistance and hydrophilicity on the surface layer and inner layer of the polymer material

TECHNICAL GIST OF THE PESENT INVENTION

2s The present invention provides an adhesion reaction method of modifying a surface layer and inner layer of C, H type and C, H, O type polymers into hydrophilic functional groups by using an Hydrogen Ion Assisted reactιon(IAR) method. More particularly, the present invention provides a method wherein by increasing the formation of hydrophi c functional groups, the functional groups formed on the surface and inner layers remain constant and the surface maintains a very stable state in the air even when the polymers in water are stored for a long period

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein

Figure 1 a is a schematic view of a device to modifying polymer surfaces according to the present invention;

Figure 1 b is a schematic view illustrating the method of the present invention,

Figure 1 c is a schematic view of a method for increasing the hydrophilicity of conventional polymer surfaces and decreasing the wetting angle thereof;

Figure 2a is a graph showing the results of the change in wetting angle with respect to energy change of ion particles which are irradiated in the existence or the nonexistence of a reactive gas using PE;

Figure 2b is a graph showing the results of the change in wetting angle with respect to energy change of ion particles which are irradiated in the existence or the nonexistence of a reactive gas using PC, Figure 2c is a graph showing the results of the change in wetting angle with respect to energy change of ion particles which are irradiated in the existence or the nonexistence of a reactive gas using PS;

Figure 2d is a graph showing the results of the change in wetting angle with respect to energy change of ion particles which are irradiated in the existence or the nonexistence of a reactive gas using PP,

Figure 2e is a graph showing the results of the change in wetting angle with respect to energy change of ion particles which are irradiated in the existence or the nonexistence of a reactive gas using PET,

Figure 3a is a graph showing the results of the change in surface energy according to the amount of ion beam with blowing oxygen by 4ml/mιn under the ion beam using PE,

Figure 3b is a graph showing the results of the change in surface io energy according to the amount of ion beam when irradiating the ion beam on a PC surface with blowing oxygen by 4ml/mιn thereon,

Figure 3c is a graph showing the results of the change in surface energy according to the amount of ion beam when irradiating the ion beam on a PS surface with blowing oxygen by 4ml/mιn thereon, i τ Figure 3d is a graph showing the results of the change in surface energy according to the amount of ion beam when irradiating the ion beam on a PP surface with blowing oxygen by 4ml/mιn thereon

Figure 3e is a graph showing the results of the change in surface energy according to the amount of ion beam when irradiating the ion 0 beam on a PET surface with blowing oxygen by 4ml/mιn thereon,

Figure 4a is a graph showing the results of the change in contact angle with the lapse of time after irradiating ion beams on a PE surface,

Figure 4b is a graph showing the results of the change in contact angle with the lapse of time after irradiating ion beams on a PC surface ι Figure 4c is a graph showing the results of the change in contact angle with the lapse of time after irradiating ion beams on a PS surface,

Figure 4d is a graph showing the results of the change in contact angle with the lapse of time after irradiating ion beams on a PP surface, Figure 4e is a graph showing the results of the change in contact angle with the lapse of time after irradiating ion beams on a PET surface,

Figure 5a is a graph showing the results of the change in contact angle with the lapse of time when a PE sample is exposed in the air,

Figure 5b is a graph showing the results of the change in contact angle with the lapse of time when a PC sample is exposed in the air

Figure 5c is a graph showing the results of the change in contact angle with the lapse of time when a PS sample is exposed in the air Figure 5d is a graph showing the results of the change in contact angle with the lapse of time when a PP sample is exposed in the air

Figure 5e is a graph showing the results of the change in contact angle with the lapse of time when a PET sample is exposed in the air,

Figure 6a is a graph showing the results of XPS analysis of carbon with respect to the generation of hydrophi c functional groups formed on the surface prior to and after modifying the surface of polymer PE

Figure 6b is a graph showing the results of XPS analysis of carbon with respect to the generation of hydrophihc functional groups formed on the surface prior to and after modifying the surface of polymer PC,

Figure 6c is a graph showing the results of XPS analysis of carbon with respect to the generation of hydrophihc functional groups formed on the surface prior to and after modifying the surface of polymer PP

Figure 6d is a graph showing the results of XPS analysis of carbon with respect to the generation of hydrophihc functional groups formed on the surface prior to and after modifying the surface of polymer PS;

Figure 6e is a graph showing the results of XPS analysis of carbon with respect to the generation of hydrophihc functional groups formed on the surface prior to and after surface modifying polymer PET, Figure 6f is a graph showing the results of SIMS analysis prior to and after modifying the surface of polymer PE using hydrogen ion beams under an oxygen atmosphere;

Figure 6g is a graph showing the result of SIMS analysis prior to and after modifying the surface of polymer PE using hydrogen ion beams under an oxygen atmosphere;

Figures 7a through 7d are views showing the images of the change in AFM surface roughness of PE prior to and after surface modifying;

Figures 7e through 7h are views showing the images of the change in AFM surface roughness of PC prior to and after surface modifying,

Figures 7ι through 71 are views showing the images of the change in AFM surface roughness of PP prior to and after surface modifying, Figures 7m through 7p are views showing the images of the change in AFM surface roughness of PS prior to and after surface modifying; and

Figures 7q through 7t are views the images of the change in AFM surface roughness of PET prior to and after surface modifying

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a method for modifying polymer surfaces by irradiating energized hydrogen ion particles on the surface of a polymer material at a distance between 15cm and 90cm, while blowing a reactive gas or gases around the surface of the polymer material under a vacuum condition. The irradiation dose of the hydrogen ion particles is 10¹⁵~10¹⁷ ions/cm², and the energy of the hydrogen ion particles is 0.5~1.5 keV. The above described energy range is appropriately set for activating the polymer surface. In addition, the amount of the reactive gas of oxygen varies according to the capacity of a vacuum pump, and the vacuum condition has a degree of vacuum around the material within the range between 3 x 10 torr and 7 < 10 torr

In the present invention, the hydrogen ion beam irradiated on the polymer surface breaks C-H or C-H-O bonds on the polymer surface, and oxygen, a reactive gas, is introduced into the surface, thereby forming a new type of chemical bond on the surface and inner layers. The hydrogen ion beam can react with oxygen gas, while breaking bonds in the layers under the surface as deep as about 100A as well as hydrophihc groups formed on the surface In particular, hydrogen, a relatively light element, is used as irradiated particles, thereby forming hydrophihc functional groups on the surface as well as penetrating into the layers under the polymer surface to activate the polymers In addition, the hydrogen reacts with the reactive gas blown onto the surface, resulting in an increase in hydrophilicity of the material and a longer life span of the modified surface. The polymer samples selected for the experiments with respect to the present invention are practical polymers widely used at present, such as polyethylene(PE), polypropylene(PP), and polystylene(PS), each of which consists of C and H, and polycarbonate(PC) and polyethyleneterephtalate(PET), each of which consists of C, H, and O. Hereinafter, the constitution and operation of the present invention will be described in detail through various experiments Contact Angle Measurement

The most widely known method of measuring the wetting angle is used to measure the increase in hydrophilicity of the polymer The term "wetting angle" is defined as the angle formed between a tangential line of a water drop on a polymer surface and the surface itself in which the water drop exists The tangential line is drawn from a point which the water drop is in contact with the surface A decrease in the wetting angle means that the attraction property of the surface to water, that is to say hydrophilicity, increases The wetting angle is measured by measuring the angle formed between the tangential line and the polymer surface using an ERMA Contact Anglemeter by a microscope after dropping 0 025 ml of three-times distilled water at four different positions on the polymer surface, and determined from a mean value of the measured values at the four positions (refer to Figure 1 c)

The results of measuring the wetting angle are shown in Figures

2a through 2e Using polymer samples treated with argon i e US

Patent No 5 965,629 polymer samples treated with lighter hydrogen ions, the change in wetting angle when blowing oxygen and carbon dioxide as reactive gases was examined

The samples were washed with distilled water and ethanol and then stored in an oven for 24 hours before modifying the samples by an hydrogen ion assisted reaction The wetting angle further increased in the case of modification with argon ion beams compared to modification with hydrogen ion beams

This result implies that, in the case the surface of the polymers are modified by the argon ion assisted reaction, the hydrophilicity improves even with a smaller amount of ions in the present invention compared to the previous wetting angle, while the wetting angle decreases only when the amount of modified ions is large in the previous invention Particularly, in the case of PE and PET, the wetting angle exhibits a high wettabihty of less than 10 degree at an amount of 1 χ10¹⁵ ions/cm² energized ions Other polymers are also all converted to the polymer surfaces having hydrophihc groups of less than 20 degree It implies that hydrogen ions, which is ultralight ions presented for the first time in the present invention, play an important role in forming reactive functional groups with reactive gas or gases by effectively cleaving the polymer chains by penetrating the inner layer of the polymer surface at a depth of hundreds of A In addition, oxygen has a high binding energy among the reactive gases which are not harmful to the human body, and thereby it tends to bond with carbon on the polymer surface Thus, it can be considered that the functional groups form hydrophihc groups on the surfaces Surface Energy Measurement

In order to clarify the change in wetting angle described above more phenomenologica y, the surface energy is calculated by measuring the wetting angle of each modified sample with water and formamide In Figures 3a through 3e, the results of the polymer surface treatment using argon(a) and hydrogen(b) ions at an ion irradiation dose of 1 χ10¹⁵ ~ 1 χ10¹⁷ ions/cm² while blowing oxygen at 4ml/mιn are represented by using the method of Owens As shown in Figure 3a, in the case (a) of PE surface-modification by blowing oxygen and energized argon ions, the dispersion force decreases approximately from 30 to 20 ergs/cm² and the surface energy increases from 30 to 35 ergs/cm², which implies very little change However, in the case (b) of hydrogen ion irradiation while blowing oxygen gas, the polar energy shows a rapid increase from 0 4 to 48 ergs/cm² when the ion dose is 1 χ10¹⁵ ions/cm², while there is no change in value of the dispersion force For this reason, the surface energy of PE increases from 30 to 70 ergs/cm² From these results, it is considered that as the formation of unstable radicals is performed without damage to the surface due to the collision between the irradiated hydrogen ions, the oxygen gases blown around the polymer react with the carbon and hydrogen ions on the polymer surface to thereby make the hydrophihc groups stable As a result the hydrophihc groups remain constant even though they are exposed to air for a long period of time The surface modification using hydrogen ion beams shows the reaction mechanism of ion assisted reaction more definitely compared to the polymer surface modification method(surface modification using argon ions) previously invented, and is an epoch-making invention which establishes the future polymer surface modification method

Figure 3b is a graph calculating the surface energy according to the argon and hydrogen ion assisted reaction of polymer material PC In the case of polycarbonate as well as PE, the dispersion force on the surface maintains a constant value prior to and after the surface modification However, in the case of modification with hydrogen ion beams, the dispersion force shows a rapid change in the region where lower energy of ions are irradiated The polar force increases by more than 16 times, i e , from 2 5 to 42 ergs/cm², and the resultant surface energy increases by more than two times, i e , from 25 to 65 ergs/cm² The improvement of the present invention compared to the previous invention (US Patent 5,965,629) is that the value of the surface energy shows a rapid increase in the region even with a lower irradiation dose of 1 χ10¹⁵ ions/cm², while, in the case of modification with argon ion beams, the surface energy increases only when irradiating a large amount of ions of more than 5x10¹⁶ ions/cm², which is closely connected with a decrease in time for surface modification It is assured that this increase in the polar force of the surface energy is due to the hydrophihc groups formed on the polymer surface by the reaction of the oxygen and hydrogen between two polar solvents Thus, the large decrease in wetting angle which occurring when oxygen is blown onto the surface during ion irradiation is caused by the increase in surface energy due to the hydrophihc groups formed on the surface

Figures 3c through 3e are graphs calculating the surface energy of surface-modified samples on the surface of the polymer materials PS, PP, and PET, respectively using argon and hydrogen ion beam assisted reactions These graphs show almost the same results with the above two results, therefore, it is considered that when the hydrogen ion beam assisted reaction is applied to polymer materials, the polymer surfaces can have hydrophihc groups In addition, many information can be obtained by measuring the surface energy, particularly the formation of the hydrophihc functional groups of the surface with regard to the polymer materials These hydrophihc functional groups are classified into two categories, one is a functional group which is formed by reacting unstable radicals on the surface with the introduced oxygen gases as the hydrogen ions are irradiated, the other is a stable functional group which is formed by binding unbound ions formed in the inner layers by the hydrogen ion irradiation with the same oxygen gases

From the information concerning the change in contact angle and the surface energy, it shows that the polar force, which is the polar bond of the surface energy's hydrogen bond, increases under the influence of the hydrophihc functional groups newly formed

The Change in Contact Angle with the Lapse of Time

To correlate the relationship with the above results and the change in contact angle, the modified samples were stored in the air and in tne water, respectively for a long period of time, the contact angle of each sample with the lapse of time were measured periodically, and the results are illustrated in Figures 4a through 4e The surface modification was performed by irradiating argon ion beams(ιon irradiation dose of 5x10¹⁶ ions/cm²) and hydrogen ion beams(ιon irradiation dose of 1 χ10¹⁶ ions/cm²), respectively while blowing oxygen gas at 4ml/mιn In the case of argon ion beam, the contact angle was lowest at ion irradiation dose of 1 χ10¹⁶ ions/cm², but the process condition was performed as described above in order to be consistent with the optimum process condition of hydrogen ion beams

Figure 4a is a graph showing the results of measuring the contact angle after removing the water adsorbed on the surface using nitrogen gas in the case of a sample stored in the water and the results of directly measuring the contact angle in the case of a sample stored in the air respectively with the lapse of a certain time while storing a PE sample in the air and in water, respectively In both cases of a sample with oxygen gas blown therein with argon and a sample with oxygen blown therein with hydrogen ion beams, when the sample is stored in the air, the contact angle is restored to the original contact angle prior to modification However, in the case of a sample stored in water, because the hydrophihc functional groups formed by ion assisted reaction remain constant without being resolved in water, the contact angle after modification remains constant The same results are stated in the documents already stored, and they prove that the hydrophihc functional groups contribute to the increase of the contact angle

PC of Figure 4b, PS of Figure 4b, and PP of Figure 4d show the same trend and, particularly in the case of PET of Figure 4e, hydrophihc s groups with a very low contact angle remain constant for a long period

Measurement of the Life Span of Hydrophihc Functional Groups

Based on the results obtained by calculating the contact angle and the surface energy, the life span of the hydrophihc functional groups io on the surface is measured by using the following method in order to predict the life span of the functional groups After measuring the contact angle each of the samples are modified by a method of introducing oxygen gas at a rate of 4ml/mιn while irradiating hydrogen ion beams of 1 χ10¹⁵ ions/cm² under the condition when the wetting i s angle of the surface is at the lowest, and then are taken out from a thermostatic bath to thereby measure the contact angle and the surface energy after a lapse of 6, 12, 24, 48, 72, 96, 144. and 199 hours. respectively

As shown in Figure 5a, in the case of argon ion irradiation or in o the case of argon ion irradiation with oxygen blown onto the surface, the contact angle shows a rapid increase with the lapse of time, while, in the case of hydrogen ion irradiation with oxygen blown onto the surface the contact angle remains between 10 and 15 degree for up to 48 hours and then continuously increases with the further lapse of time up to 50 5 degrees.

The results obtained in the case of PS(Figure 5b) and PP(Fιgure 5c) are also similar to those of polyethylene, which implies that as the hydrophihc functional groups on the surface are exposed to air, they are converted to hydrophobic groups by a chain rotation, thereby reverting back to the original contact angle On the contrary, in the case of PC(Fιgure 5b) and PET(Fιgure 5e), the contact angles immediately after surface-modification with hydrogen ion beams are 15 degrees and s 18 degrees, respectively, while the contact angles measured after the lapse of 192 hours are 33 degrees and 29 degrees, respectively Thus, the contact angle difference with the lapse of time is less than 15 degrees This is one of the unique results of the present invention, and it is considered that, in the case of PC and PET, hydrophihc groups are o increased more rapidly as a chain-scission is performed on the oxygen and carbon existing in the originally constituted binding structure by hydrogen ion beams From the above results it shows that hydrogen a lightweight ion, is a more important factor than argon or other ion beams in the formation of hydrophihc functional groups working on the s surface, and hydrogen ions serving as reactors play supplementary roles in surface-adsorption By the results of the present invention, it shows that the ion assisted reaction method is applicable to modification of the surfaces of all kinds of polymer material, and shows much better effects than the conventional polymer treatment method o X-ray Analysis

In order to determine what the hydrophihc functional groups formed on the surface consist of, the previous invention has been analyzed and many researchers are analyzing this matter In the present invention, in order to examine it by both quantitative and 5 qualitative analyses, a X-ray photoelectron spectroscopy(XPS) analysis is performed to investigate the chemical change in polymer surface The XPS analyzer used in the present experiment is the Surface Science Instrument Company's 2803-s spectrometer which uses a monochromatic light Al Kα X-ray The minimization energy and spatial resolution of a photo beam are 0 48 eV and 100μm, respectively, and the pass energies of high resolution and of low resolution are 54 eV and 156 eV, respectively s Figures 6a through 6e show the results of the above analysis, wherein (a) corresponds to modification by not using ion beams, (b) corresponds to an introduction of oxygen gas by 4ml/mιn, while irradiating hydrogen ion beams at the amount of 1 χ10¹⁵ ions/cm², and (c) corresponds to an introduction of oxygen gas by 4ml/mιn, while o irradiating hydrogen ion beams at the amount of 1 χ10¹⁶ ions/cm² respectively

Figure 6a is a spectrum of XPS Cls according to the results of introducing oxygen ions by 4ml/mιn while irradiating hydrogen ions at the amount of 1 χ10¹⁵ ions/cm² by non-irradiated PE and hydrogen ion s assisted reaction (a) is a graph of the surface of a non-modified sample and (b) is a graph of the surface modified by hydrogen ion beam assisted reaction When the peak with respect to C-C(C-H) bond at binding energy of about 285 eV is modified from an oxygen atmosphere to argon ion beams, it decreases a little and the peak width at half o height increases The remarkable thing is that bonds of a slightly higher binding energy increase This is related to C-O, C=0 bonds and it implies that oxygen bonds increase

Figure 6b is a surface analysis graph of XPS Cls showing the chemical state change of the surface of polymer PC according to ion 5 irradiation As a surface analysis of PC with oxygen blown around by 4ml/mιn at the ion irradiation dose of 1 10¹⁵ ions/cm² and of non- irradiated PC, the former PC's peak strength corresponding to C-C bond decreases compared to the non-irradiated PC Thus, the peak strength and area corresponding to C-O, C=O bonds increase greatly This change in contact angle is closely connected with the formation of hydrophihc groups on the surface

In Figure 6c, XPS measurement is performed so as to examine s whether these hydrophihc groups are formed on the PS surface or not (a) is a Cls spectrum of non-modified PS and (b) is a Cls spectrum of PS where hydrogen ions of 1 x10¹⁵ ions/cm² are irradiated on the surface thereof while blowing oxygen by 4ml/mιn The peak shown at 285 eV is a peak by C-C or C-H bonding, and it implies that, in the case io of non-modified PS, most carbon is formed by this kind of bond In addition the small peaks shown at 286 5 eV and 288 3 eV are peaks for C-O bond and C adsorbed in the air, and the reason the C-O bond exists is because of the addition agent used in the fabrication process In the case of an ion-irradiated sample, the strength of C-C peak is i s reduced, -(C-O)- peak increases, and 288 3 eV peak by -(C=O)- bonding and 290 1 eV peak by -(C=O)-O- bonding are newly formed Therefore, as described above, the change in contact angle results from the formation of -C-O-, -(C=O)-, -(C=O)-O- hydrophihc groups by chemical bonding 0 Figure 6d is the results of Cls surface analysis of non-modified

PP and of a sample where hydrogen ion beams of 1 χ10¹⁵ ions/cm² are irradiated while oxygen gas by 4ml/mιn In the case of non-modified PP it shows only a 285 eV peak which corresponds to C-C binding energy However, in the case of the sample modified by hydrogen ion assisted 5 reaction, a 286 5 eV peak corresponding to C-O binding energy and a 288 2 eV peak corresponding to C=O binding energy are newly formed From these results, it shows that, in the case of the non-modified sample, polymers are formed by carbon and hydrogen bonding alone, while, in the case of modification by hydrogen ion assisted reaction, hydrogen ions are bound on a cleaved polymer surface to thereby form hydrophihc functional groups thereon Also, in the case of hydrophihc treatment of a polymer culture dish which is previously patented, the s same results are shown, and it is proven that much more oxygen ions than those of the above case are bound and the binding state is very stable

Figure 6e is the results of XPS Cls peak surface analysis of PET material In the case of the ion irradiation dose of 1 χ10¹⁵ ions/cm², the io peak strength and area of C-O and C=O have increased as many as the above results compared to those of the non-modified sample In particular, in the case that PET material is surface-modified, the peak of C-O-O- as well as C-O and C=O is generated, the peak strength of C-O is almost similar to that of C-C, and thereby the hydrophihc groups are i s maintained by oxygen and carbon bonding under the surface layer as well as by oxygen ion bonding on the surface SIMS Analysis

Hitherto, the relation between the previously invented polymers and the present invention has been stated through quantitative analysis 0 of oxygen bound on the surface by the XPS surface analysis of hydrophihc treatment of the surface which is modified by hydrogen ion assisted reaction discussed in the present invention Since polymer materials are formed of insulating materials and thereby surface charging occurs, it is difficult to perform accurate measurement in this kind of surface analysis In particular, since it is difficult to discuss the qualitative measurement, the binding state of the hydrophihc functional groups under the surface layer as well as on the surface is examined by Secondary Ion Mass Spectroscopy(SIMS) which is another way of the surface analysis

Figure 6f is a graph showing the results of analyzing the surface of PE having the simplest bond among the five kinds of polymers discussed in the present invention The upper graph shows the SIMS analysis prior to surface-modification and the lower graph shows the SIMS analysis after surface modification When the both graphs are compared, it will be noted that the strength at the oxygen peak (16 point) of a modified sample has increased about 20 times compared to a non-modified sample The oxygen peak of the non-modified sample is a peak which is detected when oxygen adsorbed on the surface is exposed to air It is noted that the oxygen of the surface-modified sample has the strength even higher than carbon which is a structural component of polymer PE, and thereby hydrophihc functional groups are formed on the surface Figure 6g is a graph exhibiting the basis that the hydrophihc functional groups on the surface are capable of retaining for a longer time compared to surface-modification with argon ions previously patented which is the focus of the present invention And, it is an analysis graph wherein measurement is performed after depth profiling below 100A from the surface The upper graph is a depth profiling graph of the non-modified sample below the surface, and the lower graph is a depth profiling graph of the sample irradiated with ions of 1 χ10¹⁵ ions/cm² by hydrogen ion assisted reaction below the surface In the case of the non-modified sample, there are almost no oxygen ions on the surface, while, in the case of the sample modified according to the present invention, 0^2" (16 point) and 0^" (17 point) ions are bound for the most part In the case of modification with hydrogen ion beams while blowing oxygen gas, the above results work upon improving the contact angle and maintaining the hydrophihc surface according to the chain rotation because the formed hydrophihc functional groups are bound in a stable state

AFM Surface Analysis Figure 7a is a AFM surface image according to the surface- modification change when blowing oxygen by 4ml/mιn while irradiating at the amount of 1 χ10¹⁵ ~ 1 x10¹⁷ ions/cm² by a non-modified sample and hydrogen ion assisted reaction In the case of the non-modified sample, the surface is more or less rough and its ends are very sharp On the other hand, in the case of hydrogen ion beam irradiation, the acuminate parts on the surface are changed to very soft ones In the case of ion irradiation of 1 χ10¹⁵ ions/cm², the RMS surface roughness value of the surface is 247A which is the minimum value When more ions are applied to PE surface, the number of irradiating hydrogen ions increases more and more, whereby the surface roughness increases as in the case of argon or other ions As the result, the maximum value of 1030A is observed at 1 χ10¹⁷ ions/cm² From these results, it is observed that if the hydrophilicity of the surface increases, the surface roughness increases, whereby the contact angle value also increases On the contrary, when irradiating only argon ions, it was found out that if the surface energy increases, the contact angle decreases Moreover when ions are irradiated although oxygen is blown around the surface there is no difference in surface roughness compared to the case that oxygen gas is not blown around the surface It shows that a large decrease in contact angle observed in the ion-irradiated polymer while oxygen is due to not the surface roughness change, but the hydrophihc groups formed on the surface From these results, it is considered that the change in contact angle is affected by the ion-irradiated surface and the hydrophihc groups formed by oxygen reaction rather than the surface roughness change

Figures 7e through 7t are AFM analysis images of PC, PS, PP, and PET, respectively When hydrogen ion beam treatment is performed in the present invention, the surface roughness according to the ion irradiation energy is similar to that of the case of surface-modification with argon ion beams previously patented However, at a lower amount of ions, the surface roughness is low and the increase in surface hydrophilicity is high compared to the surface-modification with argon ion beams

When hydrogen ion beams are irradiated on the polymer surface of a non-modified sample, the rough parts formed on the surface are more or less flattened as the irradiation energy of ions increases, thereby forming a relatively smooth surface But, further ion irradiation is performed thereafter, the surface roughness rapidly increases again In addition, the increase in surface roughness is lowest at about 1 χ10¹⁵ ions/cm² which is a lower amount of ions The reasons thereof are that the formation of hydrophihc functional groups is best performed at the above irradiation energy and that if further ion irradiation is applied, the sputtering effect becomes dominant over the surface, whereby the reaction between the oxygen gas blown around and the polymer surface cannot proceed smoothly That is to say, if the irradiation dose of ions are too many, the polymer surface is activated to form hydrophihc functional groups on the surface, resulting in destruction of the surface structure and in a thermal loss due to the generation of carbon ultimately

When the above experiment results of the present invention are put together, the decrease of the contact angle has increased compared to the argon ion assisted reaction method Particularly, in the case that the samples are stored in the water, the hydrophihc functional groups formed on the surface and inner layers remain constant even when storing the samples for a longer time In the case that the samples are s exposed to air, PC and PET consisting of C-H-O remain very stable in the air with their recovery degree of less than 15 degree In addition, it was found that the hydrophihc functional groups on the surface are formed by reacting with oxygen through XPS and SIMS analyses Particularly, in the case of SIMS analysis, it is proven that the sample io modified by hydrogen ion assisted reaction has oxygen bond thereto about more than 20 times compared to the non-modified sample Because the ion beam energy range of the present invention is about 1 keV, it is possible to control the surface characteristics alone by attaching hydrophihc functional groups to the surface without changing i s the entire polymer structure

The present invention has the effects of minimizing the surface damage and introducing ions further in the depth direction from the polymer surface by a surface modification method using hydrogen, a lightweight element, rather than the conventional ion beams, whereby 0 molecular ring substitution is rapidly performed to form hydrophihc groups also in the layers under the surface In particular, improved hydrophilicity can be obtained at a amount of ions smaller than that of the conventional argon ions and the hydrophihc functional groups are combined together to thereby maintain the hydrophilicity of the surface 5 in the air or in the water for a long period

Claims

CLAIM

1 A method for modifying a polymer surface using hydrogen ion assisted reaction, wherein energized hydrogen ions are irradiated on the polymer surface, while blowing oxygen as reactive gas around the polymer surface under a vacuum condition

2 The method of claim 1 , wherein the irradiation dose of the hydrogen ions is 10 ⁵~10¹⁷ ions/cm²

3 The method of claim 1 , wherein the energy of the hydrogen

4 The method of claim 1 , wherein the vacuum condition has a degree of vacuum around the material between 3 <10 torr and 7*10 torr