METHOD FOR PREPARING TOPOLOGICAL ELASTOMERS WITH HIGHLY BRANCHED STRUCTURES, LOW MODULUS AND HIGH ELASTICITY

Abstract

A fabrication method and application of topological elastomers with highly branched structures, low modulus and high elasticity. The topological elastomers comprise dendritic macromolecules. The fabrication method includes direct crosslinking, post-crosslinking, grafting, and copolymerization. The performance of the elastomer can be easily tuned via changing the topology of the polymer network. The breakthrough of this invention lies in that these topological elastomers with highly branched structures are having low modulus and high elasticity, which would expand its application in the field of elastomer. Notably, the variety of topological elastomers, the versatility of curing chemistries, the availability of a wide variety of monomers, and the various polymerization methods are enabling the fabrication of topological elastomers with feasibility and efficiency.

Claims

1. A method for preparing topological elastomers, wherein the topological elastomers comprise dendritic macromolecules, the method comprising direct crosslinking, post-crosslinking, grafting, and copolymerization, wherein the direct crosslinking refers to mixing all monomers and reacting the mixture of the monomers together, and a crosslinking reaction and a branched structure formation reaction are performed simultaneously, to obtain the topological elastomers directly; the post-crosslinking refers to synthesizing the dendritic macromolecules followed by crosslinking the dendritic macromolecules with a crosslinking agent to obtain the topological elastomers; the grafting refers to grafting of unreacted monomers or pre-prepared dendritic macromolecules into a polymer network to form the topological elastomers; the copolymerization refers to copolymerizing the unreacted monomers or the pre-prepared dendritic macromolecules with the polymer network to form the topological elastomers with a single network, a double network, or a interpenetrating network.

2. The method of claim 1, wherein the dendritic macromolecules comprises terminal functional groups selected from the group consisting of amino group, hydroxyl group, allyl group, vinyl group, (meth)acrylate group, thiol group, epoxy group, carboxyl group, anhydride group, silicon-hydrogen bond, alkoxy group, and isocyanate group.

3. The method of claim 1, wherein the direct crosslinking comprises two orthogonal reactions that do not interfere with each other, wherein the two orthogonal reactions are independently selected from the group consisting of radical polymerization, cationic polymerization, anionic polymerization, coordination polymerization, and functional group reaction.

4. The method of claim 3, wherein the functional group reaction comprises reactions selected from the group consisting of Michael addition reaction of thiol/amino-ene, amine/carboxyl/anhydride-epoxy reaction, amino/hydroxy-isocyanate reaction, hydrosilylation reaction, and esterification reaction.

5. The method of claim 1, wherein the crosslinking agents of the post-crosslinking are selected from the group consisting of micromolecule/macromolecule crosslinking agent, the pre-prepared dendritic macromolecules for self-polymerization, and the pre-prepared dendritic macromolecules with different terminal functional groups for functional group reaction.

6. The method of claim 5, wherein reactions of the micromolecule/macromolecule crosslinking agent with dendritic macromolecules are selected from the group consisting of Michael addition reaction of thiol/amino-ene, amine/carboxyl/anhydride-epoxy reaction, amino/hydroxy-isocyanate reaction, hydrosilylation reaction, and esterification reaction; the self-polymerization of the pre-prepared dendritic macromolecules is selected from the group consisting of free radical self-polymerization, cationic self-polymerization, anionic self-polymerization, and coordination polymerization; the functional group reactions of the pre-prepared dendritic macromolecules with different terminal functional groups are selected from the group consisting of Michael addition reaction of thiol/amino-ene, amine/carboxyl/anhydride-epoxy reaction, amino/hydroxy-isocyanate reaction, hydrosilylation reaction, and esterification reaction.

7. The method of claim 1, wherein the grafting are selected from the group consisting of grafting of unreacted monomers to the polymer network, wherein crosslinking and the dendritic macromolecules are performed simultaneously; and grafting of the pre-prepared dendritic macromolecules into the polymer network to form the topological elastomer.

8. The method of claim 7, wherein the polymer networks are selected from the group consisting of epoxy network, polyurethane network, silicone network, polyester network, and polyacrylate network.

9. The method of claim 1, wherein the copolymerizing is selected from the group consisting of copolymerizing the unreacted monomers with the polymer network to form dendritic macromolecules; copolymerizing the prepared dendritic macromolecules with the polymer network to form the topological elastomer.

10. The method of claim 9, wherein the single network, the double network, or the interpenetrating network is formed by the copolymerization of the dendritic macromolecules and the polymer network; and a block network is formed by a stepwise copolymerization of the dendritic macromolecules and the polymer network.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 is a schematic diagram of the network structure of a typical topological elastomer.

[0046] FIG. 2 is the schematic diagram of direct crosslinking.

[0047] FIG. 3 is the schematic diagram of post-crosslinking.

[0048] FIG. 4 is the schematic diagram of grafting.

[0049] FIG. 5 is the schematic diagram of copolymerization.

DETAILED DESCRIPTION OF THE INVENTION

[0050] This invention will be described in further detail regarding the following implementation examples. It should be noted that the examples mentioned below are aimed to facilitate the understanding of this invention. The invention, however, demands protection of practice more than these examples.

[0051] A typical topological elastomer with highly branched structures that possess not only low modulus but also high elasticity is shown in FIG. 1. The schematic diagram of direct crosslinking is shown in FIG. 2. The post-crosslinking processes that using other micromolecules/macromolecules, the pre-prepared dendritic polymers, and another dendritic polymer with the different terminal functional groups as crosslinking agents, are shown in FIG. 3 respectively. The schematic diagram of grafting is shown in FIG. 4. The topological elastomers that contain a double network/interpenetrating network and block network are shown in FIG. 5.

Example 1 (Direct Crosslinking for Preparation of Topological Elastomers)

[0052] The raw materials and sources of Example 1 are shown in Table 1:

TABLE-US-00001 TABLE 1 The raw materials and sources. Name Chemical Formula Manufacturer Hexamethylene C.sub.8H.sub.12N.sub.2O.sub.2 J&K Scientific diisocyanate (HDI) Polycaprolactone C.sub.2H.sub.5C[CH.sub.2O[CO(CH.sub.2).sub.5O].sub.nH].sub.3 Sigma-Aldrich triol (PCL) (China) Ditin butyl C.sub.32H.sub.64O.sub.4Sn J&K Scientific dilaurate (DBTDL) Pentaerythritol C.sub.14H.sub.18O.sub.7 Sigma-Aldrich triacrylate (PETA) (China) 2,2′-Azobis(2- C.sub.8H.sub.12N.sub.4 J&K Scientific methylpropionitrile) (AIBN) n-Butyl acetate C.sub.6H.sub.12O.sub.2 J&K Scientific

[0053] Preparation of Topological Elastomer:

[0054] The samples were weighed according to the ratio of PCL:PETA:HDI=1:0.5:1 (molar ratio), and dissolved in an appropriate amount of butyl acetate. Then 0.5 wt % of DBTDL and 1 wt % of AIBN were added. After being stirred evenly, the mixture was poured into a mold and reacted under 70° C. for 3 hours. After the solvent was evaporated in a vacuum oven, a crosslinked topological elastomer could be obtained.

[0055] The mechanical properties of the resulting topological elastomer were measured using a universal material testing machine. The modulus, strain at break, and elastic recovery were calculated from the stress-strain curve. The modulus, strain at break, and elastic recovery of the resulting topological elastomer were 150 kPa, 800%, 90%, respectively. The branched degree was calculated from the concentration of the monomers by using the formula, branched degree=(Σ branched units+Σ end unit)/Σ repeat unit. The branched degree was 60%.

Example 2 (Post-Crosslinking, Self-Polymerization of Dendritic Macromolecules in the Formation of Topological Elastomers)

[0056] The raw materials and sources of Example 2 are shown in Table 2:

TABLE-US-00002 TABLE 2 The raw materials and sources. Name Chemical Formula Manufacturer Triallylamine C.sub.9H.sub.15N TCI (Shanghai) Development Co., Ltd. β-mercaptoethylamine C.sub.2H.sub.7NS TCI (Shanghai) Development Co., Ltd. Allyl acrylate C.sub.6H.sub.8O.sub.2 Shanghai Aladdin Biochemical Technology Co., Ltd Glycidyl methacrylate C.sub.7H.sub.10O.sub.3 TCI (Shanghai) Development Co., Ltd. Triethylamine (TEA) C.sub.6H.sub.15N TCI (Shanghai) Development Co., Ltd. Photoinitiator 2959 C.sub.12H.sub.16O.sub.4 TCI (Shanghai) Development Co., Ltd.

[0057] Preparation of Dendritic Macromolecules with Methacrylate Group as the Terminal Functional Group:

[0058] 1. The samples were weighed and mixed according to the ratio of triallylamine to allyl acrylate at 1:6 (molar ratio). In the presence of 5 wt % TEA as a catalyst, the mixture was stirred evenly and reacted for 1 h;

[0059] 2. Then, the same molar amount of β-mercaptoethylamine as the allyl acrylate, 1 wt % of photoinitiator 2959 was added into the mixture. The β-mercaptoethylamine was dissolved while reacting under the irradiation of ultraviolet light at 365 nm and heating at 40° C.;

[0060] 3. After the 3-mercaptoethylamine was completely reacted, adding 2 times amount of the allyl acrylate added in step 1, and step 1 was repeated;

[0061] 4. 2 times amount of the 3-mercaptoethylamine added in step 2 were added into the mixture, and step 2 was repeated;

[0062] 5. 4 times amount of the allyl acrylate added in step 1 were added into the mixture, and step 1 was repeated;

[0063] 6. 4 times amount of the 3-mercaptoethylamine added in step 2 were added into the mixture, and step 2 was repeated;

[0064] 7. Glycidyl methacrylate in an equimolar amount to β-mercaptoethylamine of step 6 was added into the mixture, followed by reacting at 80° C. for 1 h.

[0065] After steps 1-6, a dendritic macromolecule with amino group as the terminal functional group was prepared. After that, the amino group of the terminal functional group was transformed into methacrylate group through step 7

[0066] Preparation of Topological Elastomer:

[0067] 1 wt % of photoinitiator 2959 was added to the obtained dendritic macromolecules with methacrylate group as the terminal functional group. After being stirred uniformly, the mixture was poured into a mold, followed by crosslink curing under UV light at 365 nm for 1 minute to obtain a topological elastomer. The modulus, strain at break, and elastic recovery of the resulting topological elastomer were 100 kPa, 1000%, 85%, respectively. The branched degree was 80%.

Example 3 (Post-Crosslinking, Copolymerization of Two Dendritic Macromolecules in the Formation of Topological Elastomers)

[0068] The raw materials and sources of Example 3 are shown in Table 3:

TABLE-US-00003 TABLE 3 The raw materials and sources. Name Chemical Formula Manufacturer Triallylamine C.sub.9H.sub.15N TCI (Shanghai) Development Co., Ltd. β-Mercaptoethylamine C.sub.2H.sub.7NS TCI (Shanghai) Development Co., Ltd. Allyl acrylate C.sub.6H.sub.8O.sub.2 Shanghai Aladdin Biochemical Technology Co., Ltd Glycerol C.sub.3H.sub.8O.sub.3 TCI (Shanghai) Development Co., Ltd. Monothioglycerol C.sub.3H.sub.8O.sub.2S TCI (Shanghai) Development Co., Ltd. 2-Isocyanatoethyl C.sub.6H.sub.7NO.sub.3 Shanghai Aladdin acrylate Biochemical Technology Co., Ltd n-Hexane C.sub.6H.sub.14 Sinopharm Chemical Reagent Methanol CH.sub.4O Sinopharm Chemical Reagent Anhydrous diethyl ether C.sub.2H.sub.6O Sinopharm Chemical Reagent Dichloromethane (DCM) CH.sub.2Cl.sub.2 Sinopharm Chemical Reagent Dimethyl sulfoxide C.sub.2H.sub.6OS Sinopharm Chemical (DMSO) Reagent Triethylamine (TEA) C.sub.6H.sub.15N TCI (Shanghai) Development Co., Ltd. Photoinitiator 2959 C.sub.12H.sub.16O.sub.4 TCI (Shanghai) Development Co., Ltd.

[0069] Preparation of Dendritic Macromoplecules with Amino Group as Terminal Functional Group:

[0070] 1. The samples were weighed and mixed according to the ratio of triallylamine to allyl acrylate at 1:6 (molar ratio). In the presence of 5 wt % TEA as a catalyst, the mixture was stirred evenly and reacted for 1 h;

[0071] 2. Then, the same molar amount of β-mercaptoethylamine as the allyl acrylate, 1 wt % of photoinitiator 2959 was added into the mixture. The β-mercaptoethylamine was dissolved while reacting under the irradiation of ultraviolet light at 365 nm and heating at 40° C.;

[0072] 3. After the β-mercaptoethylamine was completely reacted, 2 times amount of the allyl acrylate were added in step 1, and step 1 was repeated;

[0073] 4. 2 times amount of the β-mercaptoethylamine added in step 2 was added into the mixture, and step 2 was repeated;

[0074] 5. 4 times amount of the allyl acrylate added in step 1 were added into the mixture, and step 1 was repeated;

[0075] 6. 4 times amount of the 3-mercaptoethylamine added in step 2 were added into the mixture, and step 2 was repeated;

[0076] After steps 1-6, a dendritic macromolecule with amino group as the terminal functional group was prepared.

[0077] Preparation of Dendritic Macromolecules with Acrylate Group as the Terminal Functional Group:

[0078] 1. In DCM, the sample was weighted according to the ratio of isocyanoethyl acrylate to glycerin at 3:1 (molar ratio). 5 wt % of TEA was added, and the mixture was stirred and reacted overnight at room temperature. After being precipitated three times in n-hexane, the product was put into a vacuum oven to evaporate the solvent residue;

[0079] 2. In DMSO, an equimolar amount of α-thioglycerol to isocyanatoethyl acrylate and 5 wt % of TEA was added. The mixture was stirred and reacted overnight at room temperature. The product was diluted with methanol and purified by precipitation using an excess amount of anhydrous diethyl ether

[0080] 3. 2 times amount of the isocyanoethyl acrylate in step 1 were added into the mixture, and step 1 was repeated;

[0081] 4. 2 times amount of the α-thioglycerol in step 2 were added into the mixture, and step 1 was repeated;

[0082] 5. 4 times amount of the isocyanoethyl acrylate in step 1 were added into the mixture, and step 1 was repeated;

[0083] 6. 4 times amount of the α-thioglycerol in step 2 were added into the mixture, and step 1 was repeated;

[0084] 7. 8 times amount of the isocyanoethyl acrylate in step 1 were added into the mixture, and t step 1 was repeated.

[0085] After the above steps, a highly branched dendritic macromolecules with acrylate group as the terminal functional group was prepared.

[0086] Preparation of Topological Elastomer:

[0087] In DMSO, the prepared dendritic macromolecules with amino group and terminal acrylate group as the terminal functional groups were mixed according to a ratio of 1:2 (molar ratio). At the presence of 5 wt % of TEA as a catalyst, the mixture was stirred evenly. The mixture was poured into the mold and reacted for 2 h at 60° C. Then, the polymer was put into a vacuum oven to evaporate the solvent residue overnight. The modulus, strain at break, and elastic recovery of the resulting topological elastomer were 80 kPa, 1200%, 80%, respectively.

[0088] The branched degree was 85%.

Example 4 (Post-Crosslinking, Micromolecules as Crosslinking Agent)

[0089] The raw materials and sources of Example 4 are shown in Table 4:

TABLE-US-00004 TABLE 4 The raw materials and sources Name Chemical Formula Manufacturer Triallylamine C.sub.9H.sub.15N TCI (Shanghai) Development Co., Ltd. β-Mercaptoethylamine C.sub.2H.sub.7NS TCI (Shanghai) Development Co., Ltd. Allyl acrylate C.sub.6H.sub.8O.sub.2 Shanghai Aladdin Biochemical Technology Co., Ltd 1,10-Decanedithiol C.sub.10H.sub.22S.sub.2 TCI (Shanghai) Development Co., Ltd. Triethylamine (TEA) C.sub.6H.sub.15N TCI (Shanghai) Development Co., Ltd. Photoinitiator 2959 C.sub.12H.sub.16O.sub.4 TCI (Shanghai) Development Co., Ltd.

[0090] Preparation of Dendritic Macromolecules with Allyl Group as the Terminal Functional Group:

[0091] 1. The samples were weighed and mixed according to the ratio of triallylamine to allyl acrylate at 1:6 (molar ratio). In the presence of 5 wt % of TEA as a catalyst, the mixture was stirred evenly and reacted for 1 h;

[0092] 2. Then, the same molar amount of β-mercaptoethylamine as the allyl acrylate, 1 wt % of photoinitiator 2959 was added into the mixture. The 3-mercaptoethylamine was dissolved while reacting under the irradiation of ultraviolet light at 365 nm and heating at 40° C.;

[0093] 3. After the 3-mercaptoethylamine was completely reacted, add 2 times amount of the allyl acrylate added in step 1, and step 1 was repeated;

[0094] 4. 2 times amount of the 3-mercaptoethylamine added in step 2 were added into the mixture, and step 2 was repeated;

[0095] 5. 4 times amount of the allyl acrylate in step 1 were added into the mixture, and step 1 was repeated;

[0096] After steps 1-5, a highly branched dendritic macromolecules with allyl group as the terminal functional group is prepared.

[0097] Preparation of Topological Elastomer:

[0098] 0.25 times (molar amount) of 1,10-decanedithiol, 1 wt % of photoinitiator 2959 were added to the highly branched dendritic macromolecules with allyl group as the terminal functional group, and were stirred well. After flattening, crosslink curing under UV light at 365 nm for 1 min, a crosslinked topological elastomer was obtained. The modulus, strain at break, and elastic recovery of the resulting topological elastomer were 100 kPa, 800%, 75%, respectively. The branched degree was 80%.

Example 5 (Grafting)

[0099] The raw materials and sources of Example 5 are shown in Table 5:

TABLE-US-00005 TABLE 5 The raw materials and sources Name Chemical Formula Manufacturer Glycerol C.sub.3H.sub.8O.sub.3 TCI (Shanghai) Development Co., Ltd. Monothioglycerol C.sub.3H.sub.8O.sub.2S TCI (Shanghai) Development Co., Ltd. 2-Isocyanatoethyl C.sub.6H.sub.7NO.sub.3 Shanghai Aladdin Acrylate Biochemical Technology Co., Ltd Acrylamide (AA) C.sub.3H.sub.5NO J&K Scientific 1,6-Hexanediol C.sub.12H.sub.18O.sub.4 J&K Scientific diacrylate (HDDA) N,N-Dimethylformamide C.sub.3H.sub.7NO Shanghai Aladdin (DMF) Biochemical Technology Co., Ltd Triethylamine (TEA) C.sub.6H.sub.15N TCI (Shanghai) Development Co., Ltd. Photoinitiator 2959 C.sub.12H.sub.16O.sub.4 TCI (Shanghai) Development Co., Ltd.

[0100] Preparation of Other Polymer Network:

[0101] 1. The sample was weighted according to a ratio of AA to HDDA at 5:1 (molar ratio) and stir well;

[0102] 2. 1 wt % of photoinitiator 2959 was added under the light-free condition and stirred well;

[0103] 3. The mixture of precursor fluid was poured into the mold, and it was irradiated with UV light at 365 nm for 1 min for crosslink curing, thus obtaining the polymer precursor network.

[0104] Preparation of Topological Elastomer:

[0105] 1. The dendritic macromolecules with acrylate group as the terminal functional group was prepared according to Example 3, and then the prepared polymer precursor network was immersed in the dendritic macromolecules for 1 h.

[0106] 2. After the polymer network was fully swelled and unwound, 5 wt % of TEA was added. The mixture was stirred well and reacted at 60° C. for 1 hour. After the unreacted monomers were replaced by DMF, the polymer network was put into a vacuum oven to evaporate DMF, thus obtaining a topological elastomer.

[0107] The modulus, strain at break, and elastic recovery of the resulting topological elastomer were 100 kPa, 600%, 80%, respectively. The branched degree was 80%.

Example 6 (Copolymerization, Double Network Topological Elastomer)

[0108] The raw materials and sources of Example 6 are shown in Table 6:

TABLE-US-00006 TABLE 6 The raw materials and sources Name Chemical Formula Manufacturer Glycerol C.sub.3H.sub.8O.sub.3 TCI (Shanghai) Development Co., Ltd. α-thioglycerol C.sub.3H.sub.8O.sub.2S TCI (Shanghai) Development Co., Ltd. 2-Isocyanatoethyl C.sub.6H.sub.7NO.sub.3 Shanghai Aladdin acrylate Biochemical Technology Co., Ltd Hexamethylene C.sub.8H.sub.12N.sub.2O.sub.2 J&K Scientific diisocyanate (HDI) Poly(tetramethyleneglycol) HO[C.sub.4H.sub.8O].sub.nH J&K Scientific (PTMG) Ditin butyl dilaurate C.sub.32H.sub.64O.sub.4Sn J&K Scientific (DBTDL) Triethylamine (TEA) C.sub.6H.sub.15N TCI (Shanghai) Development Co., Ltd. Photoinitiator 2959 C.sub.12H.sub.16O.sub.4 TCI (Shanghai) Development Co., Ltd.

[0109] Preparation of Double Network Elastomer:

[0110] 1. The dendritic macromolecules with acrylate group as the terminal functional group was prepared according to Example 3; then glycerol, PTMG, and HDI were added to the dendritic macromolecules with a ratio of 2:4:7 (molar ratio). The total mass ratio of the dendritic macromolecules and other reagents was equal;

[0111] 2. 1 wt % of DBTDL and photoinitiator 2959 were added to the above mixture of precursor fluid and stirred well;

[0112] 3. The precursor fluid was poured into the mold. The sample firstly reacted at 60° C. for 1 hour, and then are irradiated with 365 nm ultraviolet light for 1 min to crosslink curing, thus obtaining the double network elastomer.

[0113] The modulus, strain at break, and elastic recovery of the resulting topological elastomer were 200 kPa, 500%, 95%, respectively. The branched degree was 70%.