Composition and method of making shape memory polymer for biomedical applications

Abstract

Shape memory polymers (SMP) based on poly vinyl alcohol (PVA) in the presence of 2-carboxyethyl acrylate oligomers (CEA), multi-wall carbon nanotubes (MWCNTs) and cross linked by ionizing radiation were investigated. Chemical crosslinking by glutaraldehyde for PVA in the presence of CEA and MWCNTs was also studied. Radiation cross linked SMP exhibits good temperature responsive shape memory behavior as demonstrated by thermal properties of radiation investigated by dynamic mechanical analysis. Transition temperature at Tan δ of radiation cross linked SMP decreased significantly by 6 and 13° C. due to addition of MWCNTs. The developed SMP exhibited promising shape memory behavior of radiation cross linked SMP for biomedical applications between temperatures range of Tan δ. Results on the gel fraction revealed significant reduction in swelling and increase in gelation due to chemical cross linking with glutaraldehyde. The radiation cross linked SMP reached 100% gelation at an irradiation dose of 50 kGy.

Claims

1. A method of making a shape memory polymer, comprising: mixing a poly vinyl alcohol solution and a 2-carboxyethyl acrylate oligomer at a specific ratio to make solution 1; adding a carbon nano tube having a specific measurement dispersed in a specific concentration with a sodium dodecyl sulfate surfactant to the solution 1 to make solution 2; mixing a chemical crosslinking agent to solution 2 before irradiation at a certain concentration; and irradiating the solution 2 using a gamma ray source in the range of 5-100 kGy to make the shape memory polymer to be used for biomedical applications.

2. The method of making the shape memory polymer of claim 1, wherein the chemical crosslinking agent is glutaraldehyde.

3. The method of making the shape memory polymer of claim 1, wherein the certain concentration is 4 ml (25%) crosslinking agent was added to 100 ml aqueous PVA solution.

4. The method of making the shape memory polymer of claim 1, wherein the specific ratio is for poly vinyl alcohol solution and the 2-carboxyethyl acrylate oligomer is 9:1.

5. The method of making the shape memory polymer of claim 1, wherein the specific measurement of carbon nano tube is at least one a 50 and 75.

6. The method of making the shape memory polymer of claim 1, wherein the specific concentration of carbon nano tubes is 10-0.5 w v.sup.−1% with 0.5 w v.sup.−1% of the sodium dodecyl sulfate.

7. A method of making a shape memory polymer, comprising: dissolving poly vinyl alcohol solution using a water 6-14 w v.sup.−1% for 6 hours at 98° C.; mixing the poly vinyl alcohol solution with 2-carboxyethyl acrylate oligomers in ratio of 9:1 to form a solution 1; dispersing a carbon nano tube of a specific size at a concentration of 0.5 w v.sup.−1% with 0.5 w v.sup.−1% of sodium dodecyl sulfate (SDS) surfactant as stabilizing agent to form a carbon nano tube solution to form a solution 2; and mixing the solution 1 and solution 2 to form a PVA/CEA/CNT solution to form a SM-PVA film.

8. The method of making the shape memory polymer as in claim 7, further comprising: irradiating the cross linked PVA/CEA/CNT solution using 5-100 kGy to obtain a shape memory polymer.

9. The method of making the shape memory polymer as in claim 7, further comprising: mixing a glutaraldehyde solution to a PVA/CEA/CNT solution to crosslink for 36 hours at 25° C. to get a cross linked PVA/CEA/CNT solution; and irradiating the cross linked PVA/CEA/CNT solution using 5-100 kGy to obtain a shape memory polymer.

10. The method of making the shape memory polymer as in claim 9, wherein the glutaraldehyde solution is used at 25% concentration.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Example embodiments are illustrated by way of example in the accompanying Fig. and like references indicate similar elements and in which:

(2) FIG. 1 shows appearance recovery in magic mirror and shape recovery of SMP's as shown in prior art.

(3) FIG. 2 shows how dynamic mechanical action works according to prior art.

(4) FIG. 3 shows multi-walled carbon nanotubes, in one embodiment.

(5) FIG. 4 shows Multi-walled carbon nanotubes (MWCNTs) synthesized by catalytic chemical vapor deposition (CVD) process for CNT-50 and CNT-75.

(6) FIG. 5 shows degree of swelling of 6% PVA as a function of irradiation dose.

(7) FIG. 6 shows degree of swelling of 10% PVA as a function of irradiation dose.

(8) FIG. 7 shows degree of swelling of 14% PVA as a function of irradiation dose.

(9) FIG. 8 shows degree of swelling of various PVA concentrations as a function of irradiation dose.

(10) FIG. 9 shows Gel fractions (%) of various PVA concentrations as a function of irradiation dose.

(11) FIG. 10 shows degree of swelling of 10% (polyvinyl alcohol/2-carboxyethyl acrylate oligomers) (PVA/CEA) at ratio (9:1) as a function of irradiation dose.

(12) FIG. 11 shows degree of swelling of PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. PVA concentration for all compositions: 10%.

(13) FIG. 12 shows degree of swelling at saturation of PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. PVA concentration for all compositions: 10%.

(14) FIG. 13 shows degree of swelling of glutaraldehyde cross linked PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. PVA concentration for all compositions: 10%.

(15) FIG. 14 shows degree of swelling at saturation of glutaraldehyde cross linked PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. PVA concentration for all compositions: 10%.

(16) FIG. 15 shows Gel fraction (%) for Glut-PVA, Glut-(PVA/CEA) at ratio (9:1), Glut-(PVA/CEA)/CNT-50 and Glut-(PVA/CEA)/CNT-75 as a function of irradiation dose. PVA concentration for all compositions: 10%.

(17) FIG. 16 shows SEM micrographs of irradiated at 5 and 100 kGy for PVA-CNT-50 and PVA-CNT-75, X=10,000.

(18) FIG. 17 shows SEM micrographs of irradiated at 5 and 100 kGy for PVA-CEA-CNT-50- and PVA-CEA-CNT-75, X=10,000.

(19) FIG. 18 shows SEM micrographs of unirradiated and irradiated at 100 kGy for Glut-PVA and Glut-PVA-CEA, X=10,000.

(20) FIG. 19 shows SEM micrographs of unirradiated and irradiated at 100 kGy for Glut-PVA-CEA-CNT-50-and Glut-PVA-CEA-CNT-75, X=10,000.

(21) Other features of the present embodiments will be apparent from the accompanying Fig.s and from the detailed description that follows.

DETAILED DESCRIPTION

(22) This invention relates to composition of shape memory polymer (SMP) using poly (vinyl alcohol) and crosslinking agents and cross-linked by ionizing radiation, method of making it and method of using it. In the instant disclosure several embodiments for the composition and method of making shape memory polymer is described. Although the present embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments.

(23) Materials: 2-carboxyethyl acrylate oligomers, polyvinyl alcohol (PVA) Mw. 75,000 were procured from Sigma Aldrich. Carbon nanotube (CNT) Type 50 and 75 were producer: NanoKarbon, Korea nano Ind. Co., Surfactant: Sodium dodecyl sulfate (SDS, C.sub.12H.sub.25SO.sub.4Na) was procured from Sigma Aldrich, unless otherwise noted it was used as received without further purification.

(24) This invention also relates to the preparation and characterization of shape memory polymers based on chemically cross-linked poly(vinyl alcohol) (PVA) in the presence of 2-carboxyethyl acrylate oligomers (CEA), multi-wall carbon nanotubes (MWCNTs) CNT-50 and CNT-75 followed by exposure to ionizing radiation to complete the crosslinking process. In one composition carbon nano tubes 50 (CNT50) and/or carbon nano tube 75 (CNT 75) is mixed with PVA to form a shape memory polymer (SMP). Characteristics of the CNT are described in Table 1.

(25) TABLE-US-00001 TABLE 1 Characteristics and morphology of multi-wall carbon nanotubes. Property CNT 50 CNT 75 Outer diameter distribution 40-60 nm 60-80 nm Inner diameter distribution 10-30 nm 30-50 nm Length distribution under 20 μm under 20 μm

(26) Multi-walled carbon nanotubes (MWCNTs) synthesized by catalytic chemical vapor deposition (CVD) process as shown in FIG. 3. In FIG. 4 CNT 50 is shown on the left and CNT 75 is shown on the right using different magnifications to show the morphology.

(27) Method

(28) In the instant invention several formulations for SMP have been introduced. The categories are: PVA (PVA/CEA) at a ratio (9:1) (PVA/CEA)/CNT-50 (PVA/CEA)/CNT-75.

(29) Also the same formulations with addition of glutaraldehyde as crosslinking agent: Glut-PVA Glut-(PVA/CEA) at a ratio (9:1) Glut-(PVA/CEA)/CNT-50 Glut-(PVA/CEA)/CNT-75

(30) Synthesis PVA solution: PVA solution having 6, 10, 14 w v.sup.−1% concentrations (w v.sup.−1% is the amount of material in 100 mL of water) were prepared by dissolving PVA in water for 6 hours at 98° C. The prepared PVA solution was cooled to room temperature and pH of PVA solution was adjusted to 4 with HCl and stored until further use.

(31) Addition of CEA to PVA: The prepared room temperature cooled PVA solution was then mixed with 2-carboxyethyl acrylate oligomers (CEA) (MW 170) in ratio of (9:1) to make solution

(32) Preparing the MWCNT: The MWCNTs having a specific measurement such as CNT-50 and CNT-75 were added at a specific concentration of 0.5 w v.sup.−1% with 0.5 w v.sup.−1% of sodium dodecyl sulfate (SDS) surfactant as stabilizing agent to make solution 2. They were stored until further use. PVA:CEA solution 1 was prepared with and without CNT, and the mixture was stirred for 3 minutes to make solution 3 that is in the form of a homogeneous mixture. The homogeneous mixture solution 3 was then injected into certain shaped glass tubes (V-shape, coiled-shape, straight-shape and plates) with a diameter of 5 mm as SMP-PVA films. The SM-PVA films were prepared by solution casting method. The crosslinking reaction was conducted for 36 hours at room temperature (25° C.). After being washed with deionized water to neutral, the SMP-PVA films samples were dried for 48 hours at room temperature under vacuum.

(33) The formulations of PVA with CNT 50 and CNT 75 are represented in Table 2. Also the formulations of (PVA) with 2-carboxyethyl acrylate oligomers (CEA), CNT 50 and CNT 75 are presented in Table 3.

(34) The irradiation source was calibrated using aqueous ferrous sulfate (Fricke dosimetry) solution according to ASTM Standard Practice E1026, (1997). The typical dose rate was 6.90151 kGy/hour and transit dose was estimated to be 12.07 Gy/second.

(35) TABLE-US-00002 TABLE 2 Formulation for polyvinyl alcohol (PVA) with CNT 50 and CNT 75. Code Dose (kGy) Code Dose (kGy) C50-5k 5 C75- 5k 5 C50-10k 10 C75- 10k 10 C50-15k 15 C75- 15k 15 C50-20k 20 C75- 20k 20 C50-25k 25 E75- 25k 25 C50-50k 50 C75- 50k 50 C50-75k 75 C75- 75k 75 C50-100k 100 C75- 100k 100 Note: PVA concentration: 10 w v.sup.−1 %, CNT concentration: 0.5 w v.sup.−1 %.

(36) TABLE-US-00003 TABLE 3 Formulation for polyvinyl Alcohol (PVA) with 2-carboxyethyl acrylate oligomers (CEA), CNT 50 and CNT 75. Code Dose (kGy) Code Dose (kGy) E50-5k 5 E75- 5k 5 E50-10k 10 E75- 10k 10 E50-15k 15 E75- 15k 15 E50-20k 20 E75- 20k 20 E50-25k 25 E75- 25k 25 E50-50k 50 E75- 50k 50 E50-75k 75 E75- 75k 75 E50-100k 100 E75- 100k 100 PVA concentration: 10 w v.sup.−1 %, PVA:CEA ratio: 9:1, CNT concentration: 0.5 w v.sup.−1 %.

(37) Chemical crosslinking: To the above mentioned PVA-CEA, PVA-CEA-CNT-50 and PVA-CEA-CNT-75 as solution 2, glutaraldehyde at certain concentration such as 4 ml (25%) was added to 100 ml aqueous PVA solution was added and then the mixture was stirred for 3 minutes to make a homogeneous mixture. The homogeneous mixture was then injected into certain shaped glass tubes (V-shape, coiled-shape, straight-shape and plates) with a diameter of 5 mm, designed in our laboratory. The SM-PVA films were prepared by solution casting method. The crosslinking reaction (chemical crosslinking) was conducted for 36 hours at room temperature (25° C.). After being washed with deionized water to neutral, the samples were dried for 48 hours at room temperature under vacuum.

(38) Radiation crosslinking: After preparation the casted samples (SM-PVA films) without glutaraldehyde; PVA, PVA-CEA, PVA-CEA-CNT-50 and PVA-CEA-CNT-75 and the casted samples (SM-PVA films) with glutaraldehyde; The PVA-G, PVA-CEA-G, PVA-CEA-CNT-50 and PVA-CEA-CNT-75 SMP-PVA films were packaged in air into sealed polyethylene specimen bags separately and then irradiated to 5, 10, 15, 20, 25, 50, 75, 100 kGy at room temperature using 60Co gamma rays source model Gamma Cell 220 from MDS Nordion, Canada. This unit was used for all irradiation studies. The source was calibrated using aqueous ferrous sulfate (Fricke dosimetry) solution according to ASTM Standard Practice E1026, (1997). The typical dose rate was 6.90151. kGy/hour and transit dose was estimated to be 12.07 Gy/second. The radiation cross linked SM-PVA films reached 100% gelation at an irradiation dose of 50 kGy. The present invention involves a reliable method for the preparation of shape memory polymers based on chemically cross linked and radiation-cross linked poly (vinyl alcohol) (PVA).

(39) Characterization

(40) Gel fraction: The gel content (fraction) in the dried SMP samples was estimated by measuring its insoluble part after extraction in distilled water for 48 h at 60° C. Then, they were taken out and washed with hot water to remove the soluble part, dried, and weighed. The gel fraction was calculated according to Eq. (1). The ratio of the remaining mass of insoluble material (dried to constant weight in a vacuum oven) to original mass was defined as Gel (%) as follows:

(41) $\begin{array}{cc}\mathrm{Gel}\left(\%\right)=\frac{\mathrm{mass}\mathrm{of}\mathrm{residue}\left(g\right)}{\mathrm{original}\mathrm{mass}\left(g\right)}*100& \left(1\right)\end{array}$
Values above 90% can be reached and indicate a good yield of crosslinking.
100−Gel (%)=sol (%)  (2)

(42) Thermogravimetric Analysis (TGA): The thermo gravimetric analysis (TGA) for SMP was carried out using a TGA machine (Perkin Elmer TGA7, USA) from ambient temperature up to 600° C. under nitrogen atmosphere at a heating rate of 5° C./minute. Transition temperature at Tan δ of radiation cross linked SMP decreased significantly by 6 and 13° C. due to addition of MWCNTs. In addition Tan δ of SM-PVA increases as the irradiation doses increases. Depending on irradiation dose, the transition of Tan δ appears over the range from 55 to 84° C. while in the presence of CEA, it varied from 33 to 88° C. The developed compositions show promising shape memory polymer behavior of radiation cross linked SMP for biomedical applications based on the range of temperatures of Tan δ.

(43) Dynamic Mechanical Analysis (DMA): Dynamic mechanical analysis (DMA) by PerkinElmer Inc., USA, in tensile loading was used to determine the T.sub.g, onset of T.sub.g and rubbery modulus (Er) of the networks. The samples were thermally equilibrated at T.sub.low: −50° C. for 3 minutes and then heated to T.sub.high: 280° C. at a rate of 5° C./minute. Applied static force of 110 mN, dynamic force of 110 mN, frequency of 1 Hz. T.sub.g is defined to be the peak of tan delta. Samples were measured in triplicates.

(44) Scanning Electron Microscopy (SEM): An SEM, Model JSM 5800 LV from Jeol Co., Japan was used. Maximum enlargement of the SEM is 300,000 with a resolution of 3.5 nm. Both low and high vacuum measurements were performed. Prior to examination, the samples were dried under sputter-coated gold.

(45) It is well known that radiation-induced polymerization and crosslinking have advantages over chemical crosslinking and it is widely used in recent years for the synthesis of various hydrogels for biomedical applications. The absorption of water was evaluated by performing swelling tests on the PVA gel at ambient temperature. The basic feature of the hydrogel is to absorb and hold huge amount of water in its network structure. FIG. 5 shows the equilibrium swelling profile of the γ-irradiated PVA concentrations 6 w v.sup.−1% hydrogel. The equilibrium swelling response was investigated using PVA concentrations 6 w v.sup.−1% hydrogel. The samples SM-PVA were irradiated for absorbed doses of 5, 10, 15, 20, 25, 50, 75 and 100 kGy. Three samples were irradiated for each dose point. It was found that there are decreases in the swelling degree of the prepared hydrogels with the increase of the irradiation dose.

(46) FIG. 6 shows the equilibrium swelling profile of the γ-irradiated PVA at concentration of 10 w v.sup.−1% hydrogel. The equilibrium swelling response was investigated using PVA concentration of 10 w v.sup.−1% hydrogel. The samples were irradiated for absorbed doses of 5, 10, 15, 20, 25, 50, 75 and 100 kGy. Three samples were irradiated for each dose point. It is clear that with increase of the irradiation dose the swelling degree of the prepared hydrogels decreases.

(47) FIG. 7 shows the equilibrium swelling profile of the γ-irradiated PVA at concentration of 14 w v.sup.−1% hydrogel. The equilibrium swelling response was investigated using PVA concentration of 14 w v.sup.−1% hydrogel. The samples were irradiated for absorbed doses of 5, 10, 15, 20, 25, 50, 75 and 100 kGy. Three samples were irradiated for each dose point. It is clear that with increase of the irradiation dose, the swelling degree of the prepared hydrogels decreases.

(48) FIG. 8 shows the effect of various PVA concentrations of 6, 10, 14 w v.sup.−1% on degree of swelling against irradiation dose. It is clear that with increase both PVA content in the feed solution and irradiation dose, the swelling degree of the prepared hydrogels decreases.

(49) Synthetic polymer hydrogels display controlled gelation process, structure, and mechanical properties. Ionizing radiation has been found to be widely applicable in modifying the structure and properties of polymers, and can be used to tailor the performance of either bulk materials or surfaces. In practical terms, the gelation can be defined as a dose for which the smallest amount of gel can be separated from the system. Further irradiation of the sample over the gelation dose increases the amount of gel fraction, although a part of macromolecules may be still left unbound (sol fraction).

(50) FIG. 9 shows the effect of various PVA concentrations of 6, 10, 14 w v.sup.−1% on gel fractions % against irradiation dose. It is clear that with increasing of both PVA content in the feed solution and irradiation dose up to irradiation dose of 25 kGy, the gelation degree of the prepared hydrogels increases to reach 100% gelation at an irradiation dose of 50 kGy.

(51) FIG. 10 shows the equilibrium swelling profile of the γ-irradiated (PVA/CEA) at ratio (9:1) hydrogel as a function of irradiation dose. The samples were irradiated for absorbed doses of 5, 10, 15, 20, 25, 50, 75 and 100 kGy. Three samples were irradiated for each dose point. It is clear that effect of the crosslinking of PVA via irradiation in presence of CEA decrease the swelling degree of the prepared hydrogels. When an aqueous mixture of PVA/CEA is irradiated with gamma rays, simultaneous crosslinking of PVA occurred. Grafting of CEA oligomer onto the cross linked PVA polymer chains will take place simultaneously resulting in the formation of insoluble copolymer network (gel). The overall rate of these graft copolymerization processes could influence the gel fraction and swelling of the hydrogel. The stability of the prepared hydrogels against dissolution in hot water is simply known as gelation degree (El-Hag A. and Alarifi A. 2009).

(52) FIG. 11 shows the equilibrium swelling profile of the γ-irradiated PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 hydrogel as a function of irradiation dose. The samples were irradiated for absorbed doses of 5, 10, 15, 20, 25, 50, 75 and 100 kGy. Three samples were irradiated for each dose point. It is clear that effect of the crosslinking of PVA via irradiation in presence of CEA decrease the swelling degree of the prepared hydrogels. The addition of MWCNT significantly decreases the swelling of overall hydrogel. The unique properties of CNTs, such as very high surface/volume ratio, due to the chemical stability CNTs as filler affect the significant decrease in the swelling degree.

(53) FIG. 12 shows the equilibrium swelling profile of the γ-irradiated PVA, (PVA/CEA) at ratio (9:1) hydrogel as a function of irradiation dose. The samples were irradiated for absorbed doses of 5, 10, 15, 20, 25, 50, 75 and 100 kGy. Three samples were irradiated for each dose point. It is clear that the crosslinking of PVA via irradiation in presence of CEA decreases the swelling degree of the prepared hydrogels.

(54) The influence of water content on the prepared materials was investigated. FIG. 13 shows the equilibrium swelling profile of the γ-irradiated PVA hydrogel glutaraldehyde-cross linked PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. The samples were irradiated for absorbed doses of 5, 10, 15, 20, 25, 50, 75 and 100 kGy. Three samples were irradiated for each dose point. It is clear that the chemical crosslinking on PVA as well as irradiation dose significantly decrease the swelling degree of the prepared hydrogels. The addition of CEA increases the side hydroxyl groups along with the backbone formed hydrogen bonding among the adjacent chains, leaving behind a limited number of free hydroxyl groups that lie in polymer chains. The unique properties of CNTs include very high surface/volume ratio, high chemical stability, high electro-catalytic activity and high charge transfer efficiency. All the previous properties of CNTs influenced the significant decrease in the swelling degree.

(55) FIG. 14 shows the degree of swelling at saturation of glutaraldehyde cross linked PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. PVA concentration for all compositions: 10%. The samples were irradiated for absorbed doses of 5, 10, 15, 20, 25, 50, 75 and 100 kGy. Three samples were irradiated for each dose point. It is clear that the chemical crosslinking on PVA as well as irradiation dose significantly decrease the swelling degree of the prepared hydrogels. The addition of CEA increases swelling degree of the prepared hydrogels by increasing the free hydroxyl groups that lie in polymer chains. The unique properties of CNTs include very high surface/volume ratio, high chemical stability, high electro-catalytic activity and high charge transfer efficiency. All the previous properties of CNTs influenced the significant decrease in the swelling degree.

(56) The degree of gelation of the prepared SM-gel at various irradiation doses is shown in FIG. 15. The crosslinking ratio is one of the most important factors that affect the swelling of hydrogels and their biomedical applications. Highly cross linked hydrogels have a tighter structure, and swell less compared to the same hydrogels with lower crosslinking ratios. The stability of the prepared copolymer-gels against dissolution in solvent is simply known as gelation degree. As shown in FIG. 15 the degree of gelation of the γ-irradiated PVA hydrogel glutaraldehyde-cross linked PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. It is clear that effect of the chemical crosslinking on PVA as well as irradiation dose significantly increases the gel fraction degree of the prepared hydrogels. The presence of CEA hinders the mobility of the polymer chain, hence lowering the swelling ratio leading to increase of the degree of gelation. With the increase of total radiation dose up to 50 kGy, the gel fraction of the hydrogel increases up to 100% gel fraction and the soluble fraction decreases and it results in the formation of high molecular weight hydrogel. Further increase in total radiation dose has increased the network density of the hydrogels and decreased the swelling of the hydrogels.

(57) FIG. 16 SEM micrographs of irradiated at 5 and 100 kGy for PVA-CNT-50 and PVA-CNT-75, X=10,000. SEM is a powerful tool for investigating the structure of copolymers because it monitors the superficial changes of the polymer matrix. The changes in morphology of the copolymer matrix were investigated by SEM. FIG. 15 shows SEM micrographs of the poly(vinyl alcohol) in the presence of Multi-wall carbon nanotubes (MWCNTs); CNT-50 and CNT-75 irradiated to absorbed doses of 5 and 100 kGy. An important property for the preparation of SMP is the suitable distribution of filler chains within the polymeric matrix. Also the micrographs of PVA-CNT-50, PVA-CNT-75 are magnified at 10 kX. The micrographs were taken on a cut edge of the copolymers. It can be seen that, the pure PVA-CNT-50, PVA-CNT-75 have a smooth surface.

(58) FIG. 17 shows SEM micrographs of PVA in the presence of CEA, MWCNTs; CNT-50 and CNT-75 irradiated to absorbed doses of 5 and 100 kGy. The micrographs of PVA-CEA-CNT-50 and PVA-CEA-CNT-75 are magnified at 10 kX. The micrographs were taken on a cut edge of the copolymers. It can be seen that, the smoothness surface of the pure PVA-CNT-50, PVA-CNT-75, is altered when PVA(CEA) mixed with PVA-CNT-50 or PVA-CNT-75, and a rough surface was obtained. The rough surface of the grafted polymer is due to the occurrence of grafting.

(59) FIG. 18 shows SEM micrographs of unirradiated and irradiated at 100 kGy for Glut-PVA and Glut-PVA-CEA, X=10,000. FIG. 18 shows SEM micrographs of the PVA hydrogel glutaraldehyde cross linked PVA, (PVA/CEA) at ratio (9:1) unirradiated and irradiated to absorbed dose of 100 kGy. The micrographs were taken on a cut edge of the copolymers. The CEA introduced irregularities in the morphology of the PVA network. The micrographs were taken on a cut edge of the copolymers. The addition of the MWCNT (CNT-50 and CNT75) disturbed the network structure and morphology and some particles of CNTs are clear in FIG. 18 at 10 kX of magnification, with size in range 200-300 nanometers. They are probably due to some agglomerates of MWCNTs, CNT-50-G and CNT-75-G. It is observed that carbon nanotubes exhibited relatively good dispersion in SMP and were distributed randomly. It is confirmed that the size of carbon nanotubes in the material is 200-300 nanometers in diameter and several microns in length. It is evident that an interconnected conducting network has been formed in the developed SM-PVA/CNT.

(60) PVA is a typical semi-crystalline polymer; because of the hydrogen bonding between hydroxyl groups, high physical interactions between polymer chains contribute to the high storage modulus at low temperature. It can be seen that the presence of glutaraldehyde initial storage modulus of SM-PVA indicating the addition of glutaraldehyde decreases the number of hydroxyl groups and weakens the hydrogen bonding interaction.

(61) TABLE-US-00004 TABLE 4 Tan δ of glutaraldehyde cross linked PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. PVA concentration for all compositions: 10% Dose (kGy) PVA-CEA-CNT-50 PVA-CEA-CNT-75 PVA-CEA PVA 0 6 13 33 55 5 31 56 51 63 25 53 64 88 84 50 54 68 70 58 100 81 129 61 72

(62) FIG. 19 and Table 4 present Tan δ of glutaraldehyde cross linked PVA, (PVA/CEA) at ratio (9:1), (PVA/CEA)/CNT-50 and (PVA/CEA)/CNT-75 as a function of irradiation dose. It is clear that the variation of the Tan δ values was affected by the irradiation doses and the addition of CEA to the PVA network, and also addition of the MWCNT; NCT-50 and CNT-75 decreases the Tan δ due to interactions between polymer chains.

(63) In addition, it will be appreciated that the novel SMP for medical use disclosed herein may be embodied using means for achieving better material for medical use and diagnosis. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

INDUSTRIAL APPLICABILITY

(64) Shape memory polymer as medical devices offer advantages over traditional medical devices including blood vessel stents, bone implants and medical devices used for minimally invasive surgery. One of the key advantages is that, it can be implanted into the surgical site in an impermanent, compact geometry and then be initiated to deploy into a different, long-lasting geometry to attain a specific surgical goal, such as suture or soft tissue for bone grafts, plastic surgery or stents.