Method for polymerizing monomer units and/or oligomer units by means of infrared light pulses

Abstract

A method for polymerizing monomer units and/or oligomer units is disclosed. Said method is characterized in that the energy required for polymerization is introduced into the monomer units and/or oligomer units to be polymerized by means of infrared light pulses, wherein the infrared light pulses have a wavelength of 2500 to 20000 nm, an intensity of more than 10.sup.14 W/m.sup.2, a duration of more than 8 fs and less than 3 ps and a substantially linear polarization.

Claims

1. A method for polymerizing at least one of monomer units and oligomer units, wherein energy required for polymerization is introduced into at least one of the monomer units and the oligomer units to be polymerized by means of infrared light pulses, wherein the infrared light pulses have a wavelength of 2500 to 20000 nm, an intensity of more than 10.sup.14 W/m.sup.2, a duration of more than 8 fs and less than 3 ps and a substantially linear polarization.

2. The method according to claim 1, wherein the infrared light pulses additionally have a negative chirp.

3. The method according to claim 1, wherein each infrared light pulse sweeps over a spectral range of 2 to 1000 cm.sup.1.

4. The method according to claim 1, wherein the repetition rate of the infrared light pulses lies between 0.5 kHz and 200 MHz.

5. The method according to claim 1, wherein multiple superposed infrared light pulses are being used, which differ from each other in each case in at least one parameter.

6. The method according to claim 1, wherein the superposition of the infrared light pulses takes place by means of at least one optical parametric amplifier.

7. The method according to claim 1, wherein the polymerization takes place in a localized space whichreferring to the propagation direction of the infrared light pulsesis transversely smaller than 10 m and longitudinally smaller than 20 m.

8. The method according to claim 1, wherein the polymerization takes place in a solvent.

9. The method according to claim 1, wherein a polymerization reaction, taking place spontaneously, with respect to energy, after the required activation energy is provided, is influenced by application of a solvent at a ratio of 1:1 (v/m) to 10:1 (v/m) to at least one of the monomer units and the oligomer units to be polymerized in such a way that the polymerization reaction is at the least slowed down.

10. The method according to claim 1, wherein at least one of the monomer units and the oligomer units to be polymerized are basic units of a plastic material.

11. The method according to claim 1, wherein the method is executed in such a way that specific areas of a produced polymer have a higher degree of polymerization than other areas of the polymer.

12. The method according to claim 10, wherein the method is executed in such a way that a plastic material is produced which has at least an elastic area and at least a plastic area.

13. The method according to claim 1, wherein a produced polymer has anisotropic properties which in a first direction of the polymer are 50% higher or lower than the properties in a second direction.

14. The method according to claim 1, wherein a micro-structured polymer is produced.

15. The method according to claim 5, wherein the superposed infrared light pulses differ from each other regarding at least one of their spectral ranges and their polarization.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the structural formula of toluene-2,4-diisocyanate and

(2) FIG. 2 shows an example of a structured polymer.

DETAILED DESCRIPTION

(3) FIGS. 1 and 2 will be further explained in connection with the subsequent example.

Example: Polymerization of Toluene-2,4-Diisocyanate (TDI)

(4) 100 l TDI as the monomer unit to be polymerized are mixed with 1 ml anhydrous 1,4-butanediol as solvent and reaction partner, so that the result is a ratio of 10 to 1 (referring to the volume of the substances employed in each case) between the solvent and the monomer units to be polymerized. In this manner, it is attained that all the TDI molecules are actually able to react with the 1,4-butanediol, so that after completion of the polymerization reaction there is no TDI which has not reacted present anymore. As TDI is highly toxic, the presence of monomers in the polymer formed is undesirable.

(5) In order to keep diffusion effects as low as possible in the prepared solution, only a part of the solution is applied onto an object slide and subsequently exposed to the infrared light pulses to initiate the polymerization reaction

(6) A laser with an intensity of 1.810.sup.15 W/m.sup.2 is used. The output frequency of the laser is at 2280 cm.sup.1. Each laser pulse has a duration of 500 fs and sweeps over a spectral range of 100 cm.sup.1 (that is to say, it has a full width at half maximum of 100 cm.sup.1). The laser pulses applied are chirped negatively linear, so that their frequency decreases continuously from initially 2280 cm.sup.1 to 2180 cm.sup.1 during the pulse duration of 500 fs. Moreover, the light emitted by the infrared laser is linearly polarized. The repetition rate of the laser is 100 kHz, the focus is 20 m.

(7) The structural formula of TDI is illustrated in FIG. 1. The arrows next to the isocyanate groups of the TDI indicate the vibration transition dipole moment vectors of the two isocyanate groups. As these vibration transition dipole moment vectors are offset relative to each other by 90, only one of the two isocyanate groups per molecule can deliberately be excited to react by applying polarized light.

(8) A possible reaction scheme is the following: The excitation of the isocyanate groups with the infrared light pulses leads to a breaking up of the double bonds between the nitrogen atom and the carbon atom as well as between the carbon atom and the oxygen atom. The reaction with a hydroxyl group of the 1,4-butanediol then leads to a protonation of the nitrogen atom and to a formation of an additional carbon-oxygen-bond as well as to a re-formation of the double bond between the carbon atom and the oxygen atom. As a result, thus, a urethane group (NHCOO) forms. Due to the di-functionality of the TDI and of the 1,4-butanediol, linear polyurethanes can be formed in this way.

(9) In order to form a cuboid made of polyurethane having a length of 100 m, a width of approx. 1.5 m and a depth of approx. 3 m, 60 laser pulses with a simultaneous moving of the sample are required. Thus, by 3600 repetitions a cuboid having an edge length of 100 m100 m3 m can be produced.

(10) Apart from simple cuboid-shaped polymer structures, as specified previously, it is also possible to produce micro-structured polymers and microstructures within a polymer, respectively. For example, in a modification of the example, the lettering FU can be represented as a polymer, as it is illustrated in FIG. 2.