BENZOXAZINE DERIVATIVES VITRIMERS

Abstract

An ester containing benzoxazine monomer and to a process for synthesizing the monomer and to vitrimers obtained through the polymerization of the ester containing benzoxazine monomer. Also, a use of the vitrimer as a reversible adhesive, sealant, coating or encapsulating systems for substrates selected from the group consisting of a metal, polymer, glass and ceramic material

Claims

1.-20. (canceled)

21. An ester containing benzoxazine monomer of formula (I) ##STR00017## wherein, independently, at least one R* group is present in the benzoxazine cycle, and is selected from the group consisting of H, an aliphatic C.sub.1-C.sub.6 alkyl group, OH, an aliphatic C.sub.1-C.sub.6 alkoxy group, an aliphatic C.sub.2-C.sub.6 alkenyl group, an aliphatic C.sub.1-C.sub.6 alkyl or alkoxy substituted or unsubstituted phenyl group, ##STR00018## R is either selected from the group consisting of an aliphatic C.sub.1-C.sub.6 alkyl group, an aliphatic C.sub.1-C.sub.6 alkyl or alkoxy substituted or unsubstituted phenyl group, a C.sub.2-C.sub.6 alkenyl group, —(CH.sub.2).sub.n3— wherein n.sub.3 is an integer from 1 to 10, —CH(aliphatic C.sub.1-C.sub.6 alkyl group), —CH(aliphatic C.sub.1-C.sub.6 alkyl or alkoxy substituted or unsubstituted phenyl group), or R is omitted; R′ is selected from the group consisting of H, —(CH.sub.2).sub.n3—OH, and ##STR00019##  wherein n=n.sub.1=n.sub.2 and are, independently, an integer of from 1 to 3, and R, R* and n.sub.3 are as defined above; R″ is an aliphatic C.sub.1-C.sub.6 alkyl group; and p is an integer of from 1 to 50.

22. The ester containing benzoxazine monomer according to claim 21, wherein: at least one R* group is present in the benzoxazine cycle, and the R* group is selected from the group consisting of H, an aliphatic C.sub.1-C.sub.4 alkyl group, OH, an aliphatic C.sub.1-C.sub.4 alkoxy group, ##STR00020## R is either selected from the group consisting of an aliphatic C.sub.1-C.sub.3 alkyl group, an aliphatic C.sub.1-C.sub.3 alkyl or alkoxy substituted or unsubstituted phenyl group, a C.sub.2-C.sub.4 alkenyl group, —(CH.sub.2).sub.n3— wherein n.sub.3 is an integer from 1 to 6, —CH(aliphatic C.sub.1-C.sub.3 alkyl group), —CH(aliphatic C.sub.1-C.sub.3 alkyl or alkoxy substituted or unsubstituted phenyl group), or R is omitted; R′ is selected from the group consisting of H, —(CH.sub.2).sub.n3—OH, and ##STR00021## wherein n=n.sub.1=n.sub.2 and are, independently, an integer of from 1 to 3, and R, the least one R* and n.sub.3 are as defined above, and R″ is an aliphatic C.sub.1-C.sub.6 alkyl group.

23. A process for synthesizing an ester-containing benzoxazine monomer of formula (I) according to claim 21, comprising the following steps consisting of: a) reacting a phenolic acid derivative of formula (II), comprising at least one R* group, ##STR00022## with a polyfunctional molecule or oligomer of formula (III) ##STR00023## at a temperature of from 25° C. to 200° C., during 1 h-72 h, in the presence of a catalyst of Bronsted acid type, resulting in a phenol terminated oligomer or molecule of formula (IV) ##STR00024##  and b) reacting the compound of formula (IV) with a mixture of: an amino-alcohol bifunctional derivative of formula (V): ##STR00025##  and an aldehyde derivative, at a temperature range of from 25° C. to 100° C., during 0.5 h to 48 h, wherein R, R′, R″, the at least one R* group, n, n.sub.1, n.sub.2, p are, independently, as defined above, with the proviso that when the at least one R* group of the phenolic acid derivative is in ortho position with regard to —OH group, then R* is H.

24. The process according to claim 23, wherein the phenolic acid derivative is selected from the group consisting of mono-, di-, tri-hydroxybenzoic acid derivatives, anacardic acid derivatives, hydroxycinnamic acid derivatives, aliphatic X-hydroxyphenyl acid derivatives, wherein X is 2-4, aliphatic diphenolic acid derivatives and triphenolic acid derivatives, or mixtures thereof.

25. The process according to claim 24, wherein the aliphatic mono-, di-, tri-hydroxybenzoic acid derivatives are of formula (VI) ##STR00026## wherein R is omitted, and at least one of R.sub.1 to R.sub.5 corresponds to R*, and at least one among R.sub.1-R.sub.5 is selected from the group consisting of 1, 2 and 3 hydroxyl group(s), then at least one H is in phenolic ortho-position, the rest being at least one of H and an aliphatic alkyl group of C.sub.1-C.sub.6.

26. The process according to claim 24, wherein the anacardic acid derivatives are of formula (VII), wherein R.sub.6═R*, ##STR00027## wherein R is omitted, and R.sub.6 is ##STR00028##

27. The process according to claim 24, wherein the hydroxycinnamic acid derivatives are of formula (VIII) ##STR00029## wherein at least one of R.sub.1 to R.sub.5 corresponds to R*, and at least one among R.sub.1-R.sub.5 is selected from the group consisting of 1 and 2 hydroxyl group(s) and at least one H being in phenolic ortho-position, the rest being at least one of H and an aliphatic alkyl or alkoxy group of C.sub.1-C.sub.6.

28. The process according to claim 24, wherein the aliphatic X-hydroxyphenyl acid derivatives are selected from the group consisting of aliphatic di-hydroxyphenyl acids (X=2), aliphatic tri-hydroxyphenyl acids (X=3) and aliphatic tetra-hydroxyphenyl acids (X=4) of formula (IX), or mixtures thereof ##STR00030## wherein R.sub.7, corresponding to R, independently of the nature of X-hydroxyphenyl aliphatic acid derivatives, is selected from the group consisting of (CH.sub.2).sub.n4, CH(CH.sub.2).sub.n5-(aliphatic C.sub.1-C.sub.6 alkyl or alkoxy substituted or unsubstituted phenyl group), wherein n.sub.4 is an integer from 1 to 12, n.sub.5 is an integer from 0 to 12, CH(CH.sub.2).sub.n5(CH.sub.3), CH(CH(CH.sub.3).sub.2), C(CH.sub.3).sub.2, CH(aliphatic C.sub.1-C.sub.6 alkyl or alkoxy substituted or unsubstituted phenyl group); the number of R* in the ring is depending on the number of hydroxyl groups in the ring, and at least one R* is H towards the phenolic ortho-position, and, independently, is selected from the group consisting of (CH.sub.2).sub.n4CH.sub.3, (CH.sub.2).sub.n4-(aliphatic C.sub.1-C.sub.6 aliphatic alkyl or alkoxy substituted or unsubstituted phenyl group), wherein n4 is an integer from 1 to 12, and (CH.sub.2).sub.n4(CH(CH.sub.3).sub.2); and the integer q is comprised between 1 and 3.

29. The process according to claim 24, wherein the aliphatic diphenolic acid derivatives are of formula (X) ##STR00031## wherein on each respective phenolic cycle, at least one R* is H towards the phenolic ortho-position, and otherwise R* and R.sub.2, independently, are selected from the group consisting of (CH.sub.2).sub.n4CH.sub.3, (CH.sub.2).sub.n4-(aliphatic C.sub.1-C.sub.6 aliphatic alkyl or alkoxy substituted or unsubstituted phenyl group), wherein n.sub.4 is an integer from 1 to 12, and (CH.sub.2).sub.n4(CH(CH.sub.3).sub.2), and R.sup.1 is selected from the group consisting of (CH.sub.2).sub.n5, wherein n.sub.5 is an integer from 1 to 3, CH(CH.sub.2).sub.n5(CH.sub.3), CH(CH(CH.sub.3).sub.2) and C(CH.sub.3).sub.2.

30. The process according to claim 23, wherein the compound of formula (III) has p values of 1-30, and represents, when R′═H, a polyethylene glycol (PEG) with a molecular weight (MW) in the range of from 4 MW of the C.sub.2H.sub.4O unit to 50 MW of the C.sub.2H.sub.4O unit.

31. The process according to claim 23, wherein the step a) is carried out at a temperature in the range of 60° C. to 150° C., and is performed from 12 h to 48 h.

32. The process according to claim 23, wherein the respective stoichiometry of starting reactants on step a), phenolic acid derivative: olyfunctional molecule or oligomer is 1.0-3.0 eq.:1.0 eq., resulting in an 1.0 eq. of phenol terminated oligomer or molecule of formula (IV).

33. The process according to claim 23, wherein the amino-alcohol bifunctional derivative of formula (V) includes a linear amino-alcohol derivative with a primary amine moiety and an aliphatic hydroxyl moiety, and is selected from the group consisting of 2-aminoethanol, 2-amino-2-methylpropanol, 5-aminopentan-1-ol, heptaminol and diglycolamine.

34. The process according to claim 23, wherein the aldehyde derivative is selected from the group consisting of formaldehyde, paraformaldehyde of formula ##STR00032## where m is an integer of from 8 to 100, acetaldehyde, propionaldehyde, butylaldehyde, polyoxymethylene and aldehydes having the general formula R.sub.9CHO, where R.sub.9 is a substituted or unsubstituted aliphatic C.sub.1-C.sub.20 alkyl group optionally containing heteroatoms, or mixtures thereof.

35. The process according to claim 23, wherein step b) is performed without any catalyst.

36. The process according to claim 23, wherein, when step b) includes at least one catalyst, said least one catalyst is selected from the group consisting of Zn(II)(R.sub.10).sub.2 wherein R.sub.10 is Cl.sup.−, CH.sub.3CO.sub.2.sup.−, CH.sub.3—C(═O)—O.sup.−, CH.sub.3COCHCOCH.sub.3.sup.−, CH.sub.3(CH.sub.2).sub.r:1-15CH.sub.2CO.sub.2.sup.−; triazobicyclodecene (TBD); triphenylphosphine (PPh.sub.3) and para-toluene sulfonic acid (APTS).

37. The process according to claim 23, wherein the respective stoichiometry of starting reactants on step b), phenol terminated oligomer or molecule: amino-alcohol bifunctional derivative:aldehyde derivative is 1.0 eq.:1.0-18.0 eq.:2.0-36.0 eq., resulting in an 1.0 eq. of the ester-containing benzoxazine monomer.

38. A process for preparing polybenzoxazine derivative vitrimers comprising the step of polymerization of an ester-containing benzoxazine monomer of claim 21, at temperatures within the range of from 100° C. to 250° C. for 1 h to 24 h.

39. A polybenzoxazine derivative vitrimer, that may be obtained by the process according to claim 38, exhibiting at least one of the following characteristics: (i) T.sub.v values of from 120° C. to 220° C.; and (ii) Relaxation temperature values, ≥T.sub.v values, of from 120° C. to 270° C.

40. The polybenzoxazine derivative vitrimer according to claim 39, exhibiting at least one of the following characteristics selected from the group consisting of: a relaxation time of from 0.5 s to 2 h; an activation energy related to relaxation times of from 50 kJ/mol to 200 kJ/mol; and a processing temperature of from 100° C. to 250° C.

Description

DRAWINGS

[0133] Other features and advantages of the present invention will be readily understood from the following detailed description and drawings among them:

[0134] FIG. 1 exemplarily shows a synthesis reaction of an ester-containing benzoxazine monomer from 4,4-Bis(4-hydroxyphenyl)valeric acid (DPA) as a phenolic acid derivative, in accordance with various embodiments of the invention.

[0135] FIG. 2 exemplarily shows a network for a vitrimer obtained through the curing of the valeric acid benzoxazine monomer (schematized form), in accordance with various embodiments of the invention.

[0136] FIG. 3 is an exemplary NMR spectrum of the valeric acid derivative benzoxazine monomer (PEG-DPA-mea), in accordance with various embodiments of the invention.

[0137] FIG. 4a) exemplarily displays the DSC curve and FIG. 4b) the TGA of valeric acid benzoxazine monomer, in accordance with various embodiments of the invention.

[0138] FIG. 5 exemplarily illustrates the ability of the vitrimer of FIG. 2 to be reshaped and reprocessed, in accordance with various embodiments of the invention.

[0139] FIG. 6a) exemplarily displays a Dilatometry curve (dL/L.sub.0 (%) vs temperature) of the vitrimer obtained through the curing of the valeric acid benzoxazine monomer, the latter obtained without the use of any catalyst or with the use of 2% Zn(OAc).sub.2 catalyst in step b); and FIG. 6b) exhibits the mechanical properties of the vitrimer, in accordance with various embodiments of the invention.

[0140] FIG. 7a) exemplarily depicts shear stress relaxation experiments: normalized relaxation modulus as a function of time between 120° C. and 170° C.; FIG. 7b): Arrhenius plot of the measured relaxation times for the vitrimer of FIG. 2, in accordance with various embodiments of the invention.

[0141] FIG. 8a) and FIG. 8b) are exemplary respectively displaying the NMR spectrum of the valeric acid benzoxazine monomers (PEG.sub.200-DPA-mea and PEG.sub.2000-DPA-mea), in accordance with various embodiments of the invention.

[0142] FIG. 9 exemplarily displays the DSC curve of PEGn-DPA-mea ester-containing benzoxazine monomers (n=200 and 2000), in accordance with various embodiments of the invention.

[0143] FIG. 10 exemplarily shows the Isothermal rheology monitoring of PEGn-DPA-mea ester-containing benzoxazine monomers (n=200 and 2000), in accordance with various embodiments of the invention.

[0144] FIG. 11 exemplarily displays Dilatometry curves of PEGn-DPA-mea ester-containing benzoxazine monomers (n=200 or 2000), in accordance with various embodiments of the invention.

[0145] FIGS. 12a) and 12b) are exemplary respectively showing Stress relaxation curves of poly(PEG.sub.200-DPA-mea) and poly(PEG.sub.2000-DPA-mea) ester-containing benzoxazine vitrimers, in accordance with various embodiments of the invention.

[0146] FIG. 13 exemplarily shows the Arrhenius plot of poly(PEGn-PA-mea) ester-containing benzoxazine vitrimer, in accordance with various embodiments of the invention.

[0147] FIG. 14 exemplarily displays the NMR spectrum of PEG.sub.400-PA-mea ester-containing benzoxazine monomer (PA: phloretic acid), in accordance with various embodiments of the invention.

[0148] FIG. 15 exemplarily displays DSC curve of PEG.sub.400-PA-mea ester-containing benzoxazine monomer (PA: phloretic acid), in accordance with various embodiments of the invention.

[0149] FIG. 16 exemplarily shows Isothermal rheology monitoring of PEG.sub.400-PA-mea ester-containing benzoxazine monomer (PA: phloretic acid), in accordance with various embodiments of the invention.

[0150] FIG. 17a) exemplarily illustrates stress relaxation curves and b) Arrhenius plot of poly(PEG.sub.400-PA-mea) ester-containing benzoxazine vitrimer (PA: phloretic acid), in accordance with various embodiments of the invention.

DETAILED DESCRIPTION

Example 1

Synthesis of an Ester-Containing Benzoxazine Monomer from 4,4-Bis(4-hydroxyphenyl)valeric Acid (DPA) as a Phenolic Acid Derivative

[0151] Ester-containing benzoxazine monomer was synthesized in two stages (FIG. 1).

[0152] The first step, step a), corresponds to a Fischer esterification between polyethylene glycol (PEG) (M.sub.n=400 g.Math.mol.sup.−1, p=8-9, 1 eq, 10 g) and 4,4-Bis(4-hydroxyphenyl)valeric acid (DPA) (2 eq, 14.32 g) in presence of p-toluene sulfonic acid (pTSA) introduced in catalytic amount (1 wt %). PEG, DPA and pTSA were reacted together in melt at 130° C. and agitated by mechanical stirring for 24 hours, to provide 4,4-Bis(4-hydroxyphenyl)valeric ester terminated polyethylene glycol (PEG-DPA).

[0153] The second step, step b), corresponds to a Mannich condensation between 4,4-Bis(4-hydroxyphenyl)valeric ester terminated polyethylene glycol (PEG-DPA) (1 eq, 22.8 g), ethanolamine (mea) (4 eq, 5.95 g) and paraformaldehyde (PFA) (8 eq, 5.84 g). In some examples, step b), is performed in presence of 2 wt % of Zn(OAc).sub.2 catalyst. All these reactants were reacted together in melt at 85° C. and agitated by mechanical stirring for 2 hours to provide the ester-containing benzoxazine monomer named PEG-DPA-mea.

[0154] The FIG. 3 is displaying the NMR spectrum (AVANCE III HD Bruker spectrometer) of PEG-DPA-mea ester-containing benzoxazine monomer synthesized in presence of 2 wt % of Zn(OAc).sub.2 catalyst in step b).

[0155] FIGS. 4a) and 4b) are respectively displaying the DSC and the TGA curves of the PEG-DPA-mea monomer in the presence (solid line) or in the absence (dash line) of Zn(OAc).sub.2 catalyst. Conditions: 10° C. min.sup.−1, N.sub.2 atmosphere.

[0156] The DSC curve (FIG. 4a) (Netzsch DSC 204 F1 Phoenix apparatus) shows an exothermic peak starting at a temperature of 105° C., with a maximum located at 174° C. This peak corresponds to the ring opening of the benzoxazine rings upon heating. The second peak corresponds to the thermal decomposition of the ester linkage confirmed by TGA experiment (FIG. 4b)(mass loss≈6%). The second degradation stage is very similar to both samples with a weight loss of 46.7% and a maximum degradation temperature around T32 379° C. However, it should be noticed that the presence of catalyst slightly provided a better char yield (25.1%). At this stage, the material is therefore considered thermally stable up to at least 250° C. (T.sub.d5%).

Example 2

Synthesis of a Vitrimer Obtained Through the Curing of the PEG-DPA-mea Monomer

[0157] The benzoxazine monomer obtained in Example 1 was polymerized in a Teflon® mold at 150° C. during 1 h, allowing the benzoxazine rings to open and to react on themselves to form a 3D network vitrimer (FIG. 2). Once cooled, the shape of the material is kept even after few months. Once re-heated to at least 100° C. for a few minutes, the ester bonds are exchanging with the aliphatic hydroxyl group allowing the material to be reshaped, recycled, or reprocessed; while keeping structural integrity and number of covalent bound. Considering that Mannich condensation reaction was quantitative, nearly two hydroxyls groups could react with each ester bound through transesterification reaction (even after curing). The vitrimer behaviour strongly depend on the vitrimer glass transition (T.sub.v) also considered as the temperature where the transesterification reaction significantly increased. The vitrimer behaviour of these samples was demonstrated through several experiments. After the curing step, by heating this material above the T.sub.v, the initial rod shape of the material can be designed to other original shape. Finally, the materials were ground to a powder and can be reshaped or reprocessed at 150° C. in a couple of minutes. However, its shape remains stable at room temperature as reported in FIG. 5.

[0158] Swelling experiments were performed in acetone, chloroform and water to assess the formation of a cross-linked network of the vitrimer obtained through the curing of the PEG-DPA-mea monomer. Chloroform was the highest solvent in which the vitrimer showed the highest swelling ratio (≈100%). In acetone and water, vitrimers samples swell of 40 and 20%, respectively.

[0159] The material reacted with acetic acid to form an orange turbid suspension. The chemical decomposition of thermosets is an interesting recycling process.

[0160] Dilatometry experiments is a classical tool to reveal glass transition (T.sub.g) and the vitrimer glass like transition (T.sub.v) of a vitrimer.

[0161] The device used is the Netzsch DIL 402 C apparatus with experimental conditions of 2° C. min.sup.−1, N.sub.2 atmosphere.

[0162] Two vitrimer samples were used, one obtained through the curing of PEG-DPA-mea monomer without the use of any catalyst in step b) (dash line) and the second one with the use of 2% Zn(OAc).sub.2 catalyst in step b) (solid line), results are depicted in FIG. 6. The plateau observed in for the catalyzed system is characteristic of the glass-like nature of the T.sub.v.

[0163] Mechanical properties were determined by rheological measurements recorded on Anton Paar Physica MCR 302 rheometer in rectangular-torsion mode with experimental conditions of γ=0.1% constant deformation, f=1 Hz. The T.sub.gs determined from the maximum in the loss modulus (G″) and the maximum of the loss factor (tan δ) are 59 and 93° C. respectively.

[0164] Viscoelastic properties of PEG-DPA-mea vitrimer were studied by stress relaxation experiments (FIG. 7a). The relaxation time of the polymer was clearly noticeable and proportionally decreasing upon heating from 120° C. (320 min) to 170° C. (94 s).

[0165] The temperature dependence of the relaxation time is plotted in FIG. 7b) following the Arrhenius law. The trend line in this plot fit to a thermally activated behavior for the relaxation time. The high correlation coefficient (R.sup.2=0.987) means that these data are perfectly fitting the Arrhenius law. The activation energy from the Arrhenius equation was extracted using the slope of the trend line. The activation energy obtained from stress relaxation for PEG-DPA-mea vitrimer is 155 kJ.Math.mol.sup.−1.

Example 3

Synthesis of an Ester-Containing Benzoxazine Monomer from 4,4-Bis(4-hydroxyphenyl)valeric Acid (DPA) as a Phenolic Acid Derivative and Different Molecular Weight of Poly(ethylene glycol) (PEG) Solutions

[0166] The first step, step a), corresponds to a Fischer esterification between polyethylene glycol (PEGn) (Mn=200 or 2000 g.Math.mol.sup.−1, p=4-5 or 45-46 respectively, 1 eq, 10 g) and 4,4-Bis(4-hydroxyphenyl)valeric acid (DPA) (2 eq, 28.63 and 2.86 g, respectively for PEG.sub.200 and PEG.sub.2000) in presence of p-toluene sulfonic acid (pTSA) introduced in catalytic amount (1 wt %). PEG.sub.n, DPA and pTSA were reacted together in melt at 130° C. and agitated by mechanical stirring for 24 hours, to provide 4,4-Bis(4-hydroxyphenyl)valeric acid terminated polyethylene glycol (PEGn-DPA, wherein n=200 or 2000).

[0167] The second step, step b), corresponds to a Mannich condensation between 4,4-Bis(4-hydroxyphenyl)valeric ester terminated polyethylene glycol (PEG.sub.n-DPA) (1 eq, 25 mmol, 18.2 or 63.1 g, respectively for PEG.sub.200 and PEG.sub.2000), ethanolamine (mea) (4 eq, 100 mmol, 6.11 g) and paraformaldehyde (PFA) (8 eq, 200 mmol, 6.0 g). All these reactants were reacted together in melt at 85° C. and agitated by mechanical stirring for 2 hours to provide the ester-containing benzoxazine monomer named PEG.sub.n-DPA-mea. The reaction product was used without further purifications for the elaboration of vitrimer materials.

[0168] The FIG. 8a) and FIG. 8b) are respectively displaying the NMR spectrum (AVANCE III HD Bruker spectrometer) of PEG.sub.200-DPA-mea and PEG.sub.2000-DPA-mea ester-containing benzoxazine monomers.

[0169] FIG. 9 is displaying the DSC curves of the PEG.sub.200-DPA-mea and PEG.sub.2000-DPA-mea monomers. Conditions: 10° C. min.sup.−1, N.sub.2 atmosphere (Netzsch DSC 204 F1 Phoenix apparatus). The DSC curve shows an exothermic peak starting at a temperature of 105 and 120° C. for PEG.sub.200-DPA-mea and PEG.sub.2000-DPA-mea, respectively. This peak corresponds to the ring opening of the benzoxazine rings upon heating. The second peak corresponds to the thermal decomposition of the ester linkage.

[0170] The curing of the PEGn-DPA-mea ester-containing benzoxazine monomers was monitored by rheological measurement depicted in FIG. 10, to assess the mechanical behaviour of the monomers during the curing process.

[0171] The rheogram is performed under the following conditions: 1 Hz, with linear amplitude from 1 to 0.1%; 25 mm plates. The test is performed following a heating ramp from 80° C. to 140° C. at 15° C./min followed by an isothermal measurement at 140° C. The storage and loss modulus are recorded as a function of time. The term “gelation time” is defined as the time when the storage and the loss modulus of the soften monomer increases abruptly to transform into a gel. The gelation is defined by the crossover point between the storage and the loss modulus. At 140° C., the gelation time is reached after 116 s and 864 s, respectively for PEG.sub.200 and PEG.sub.2000.

Example 4

Synthesis of a Vitrimer Obtained Through the Curing of PEGn-DPA-mea Ester-Containing Benzoxazine Monomers

[0172] The benzoxazine monomers obtained in Example 3 was polymerized in a Teflon mold at 150° C. during 1 h for the obtention of a PEG.sub.n-DPA-mea derivatives polybenzoxazine vitrimer material (n=200 or 2000).

[0173] Swelling experiments were performed in water to assess the formation of a cross-linked network of the vitrimer obtained through the curing of the PEG.sub.n-DPA-mea monomer. Vitrimers samples swell of 10% and 200%, respectively for PEG.sub.200 and PEG.sub.2000.

[0174] Dilatometry thermograms of the vitrimer samples are reported in FIG. 11. The device used is the Netzsch DIL 402 C apparatus with experimental conditions of 2° C. min.sup.1, N.sub.2 atmosphere. The first plateau corresponds to the T.sub.g of material while the second is characteristic of the glass-like nature of the T.sub.v.

[0175] Viscoelastic properties of poly(PEG.sub.n-DPA-mea) vitrimer were studied by stress relaxation experiments (FIG. 12a): poly(PEG.sub.200-DPA-mea) vitrimer and FIG. 12b): poly(PEG.sub.2000-DPA-mea) vitrimer). The relaxation time of the polymer was clearly noticeable and proportionally decreasing upon heating from 150° C. (814 s) to 170° C. (208 s) for PEG.sub.200-DPA-mea and from 130° C. (315 s) to 150° C. (36 s) for PEG.sub.2000-DPA-mea.

[0176] The temperature dependence of the relaxation time was plotted following the Arrhenius law in FIG. 13. The trend line fits to a thermally activated behaviour for the relaxation time. The high correlation coefficient (R.sup.2=0.9996 and 0.9817 respectively for PEG.sub.200 and PEG.sub.2000) means that these data are perfectly fitting the Arrhenius law. The activation energy from the Arrhenius equation was extracted using the slope of the trend line. The activation energy obtained from stress relaxation is 106 and 154 kJ.Math.mol.sup.−1 respectively for poly(PEG.sub.200-DPA-mea) and poly(PEG.sub.2000-DPA-mea) vitrimer.

Example 5

Synthesis of a Benzoxazine Monomer from Phloretic Acid as a Phenolic Acid Derivative

[0177] The first step, step a), corresponds to a Fischer esterification between polyethylene glycol (PEG.sub.400) (M.sub.n=400 g.Math.mol.sup.−1, p=8-9, 1 eq, 10 g) and phloretic acid (PA) (2 eq, 8.31 g) in presence of p-toluene sulfonic acid (pTSA) introduced in catalytic amount (1 wt %). PEG.sub.400, PA and pTSA were reacted together in melt at 110° C. and agitated by mechanical stirring for 24 hours, to provide phloretic acid terminated polyethylene glycol (PEG.sub.400-DPA).

[0178] The second step, step b), corresponds to a Mannich condensation between phloretic acid terminated polyethylene glycol (PEG.sub.400-PA) (1 eq, 17.3 g), ethanolamine (mea) (2 eq, 3.04 g) and paraformaldehyde (PFA) (4 eq, 2.98 g). All these reactants were reacted together in melt at 85° C. and agitated by mechanical stirring for 2 hours to provide the ester-containing benzoxazine monomer named PEG.sub.400-PA-mea. The reaction product was used without further purifications for the elaboration of vitrimer materials.

[0179] FIG. 14 is displaying the NMR spectrum (AVANCE III HD Bruker spectrometer) of PEG.sub.400-PA-mea ester-containing benzoxazine monomer.

[0180] FIG. 15 is displaying the DSC curve of the PEG.sub.400-PA-mea monomer. Conditions: 10° C. min.sup.−1, N.sub.2 atmosphere (Netzsch DSC 204 F1 Phoenix apparatus). The DSC curve shows an exothermic peak starting at a temperature of 132° C. for PEG.sub.400-PA-mea. This peak corresponds to the ring opening of the benzoxazine rings upon heating. The second peak corresponds to the thermal decomposition of the ester linkage.

[0181] The curing of the PEG.sub.400-PA-mea ester-containing benzoxazine monomer was monitored by rheological measurement in FIG. 16, to assess the mechanical behaviour of the monomers during the curing process.

[0182] The rheogram is performed under the following conditions: 1 Hz, with linear amplitude from 1 to 0.1%; 25 mm plates. The test is performed following a heating ramp from 80° C. to 140° C. at 15° C./min followed by an isothermal measurement at 140° C. The storage and loss modulus are recorded as a function of time. The term “gelation time” is defined as the time when the storage and the loss modulus of the soften monomer increases abruptly to transform into a gel. The gelation is defined by the crossover point between the storage and the loss modulus. At 140° C., the gelation time is reached after 27 min.

Example 6

Synthesis of a Vitrimer Obtained through the Curing of PEG400-PA-mea Ester-Containing Benzoxazine Monomers

[0183] The benzoxazine monomer obtained in Example 5 was polymerized in a Teflon mold at 150° C. during 1 h for the obtention of a PEG400-PA-mea derivatives polybenzoxazine vitrimer material.

[0184] Viscoelastic properties of poly(PEG400-PA-mea) vitrimer were studied by stress relaxation experiments (FIG. 17a)). The relaxation time of the polymer was clearly noticeable and proportionally decreasing upon heating from 120° C. (1131 s) to 170° C. (14 s).

[0185] The temperature dependence of the relaxation time was plotted following the Arrhenius law (FIG. 17b)). The trend line fits to a thermally activated behaviour for the relaxation time. The high correlation coefficient (R.sup.2=0.9901) means that these data are perfectly fitting the Arrhenius law. The activation energy from the Arrhenius equation was extracted using the slope of the trend line. The activation energy obtained from stress relaxation is 131 kJ.Math.mol.sup.−1.