PVDF-TrFE co-polymer having improved ferroelectric properties, methods of making a PVDF-TrFE co-polymer having improved ferroelectric properties and methods of changing the end group of a PVDF-TrFE co-polymer
A method of exchanging or transforming end groups in and/or improving the ferroelectric properties of a PVDF-TrFE co-polymer is disclosed. A bulky or chemically dissimilar end group, such as an iodine, sulfate, aldehyde or carboxylic acid end group, may be transformed to a hydrogen, fluorine or chlorine atom. A method of making a PVDF-TrFE co-polymer is disclosed, including polymerizing a mixture of VDF and TrFE using an initiator, and transforming a bulky or chemically dissimilar end group to a hydrogen, fluorine or chlorine atom. A PVDF-TrFE co-polymer or other fluorinated alkene polymer is also disclosed. The co-polymer may be used as a ferroelectric, electromechanical, piezoelectric or dielectric material in an electronic device.
1. A random PVDF-TrFE co-polymer comprising a plurality of vinylidene fluoride units and a plurality of trifluoroethylene units, having a molecular weight of from 200 kDa to less than 600 kDa and a formula X 1 —(C 2 H 2 F 2 ) p —(C 2 HF3) q —X 2 , where X 1 is selected from R, H, F and Cl, R is a C n -alkyl group that may contain from 1to 2n+1 fluorine atoms, X 2 is independently H, F or Cl, n is an integer of 1 to 6, p and q are integers of 2 or more, and p+q>2000, wherein the PVDF-TrFE co-polymer has a greater solubility than and ferroelectric properties similar to a PVDF-TrFE co-polymer having a molecular weight of 600 kDa or more and an end group or substituent chemically dissimilar from H, F and Cl.
2. The PVDF-TrFE co-polymer of claim 1 , wherein the molecular weight is from 100-300 kDa.
3. The PVDF-TrFE co-polymer of claim 1 , wherein p+q>2500.
4. The PVDF-TrFE co-polymer of claim 3 , wherein p+q<20,000.
5. The PVDF-TrFE co-polymer of claim 1 , wherein p and q are in a ratio of from 10:90 to 90:10.
6. The PVDF-TrFE co-polymer of claim 1 , wherein the PVDF-TrFE co-polymer comprises a fluorinated polyalkene having a ratio of F atoms to H atoms of from 7:5 to 2:1.
7. The PVDF-TrFE co-polymer of claim 1 , wherein X 1 is R, H or Cl and X 2 is independently H or Cl.
8. The PVDF-TrFE co-polymer of claim 7 , wherein X 1 is R or H and X 2 is H.
9. The PVDF-TrFE co-polymer of claim 8 , wherein X 1 is a C 1-4 alkyl group that contains from 3 to 2n+1 fluorine atoms.
10. The PVDF-TrFE co-polymer of claim 8 , wherein each of X 1 and X 2 is H.
11. The PVDF-TrFE co-polymer of claim 4 , wherein p+q≥3000.
12. The PVDF-TrFE co-polymer of claim 11 , wherein p+q≤15,000.
13. The PVDF-TrFE co-polymer of claim 12 , wherein p+q≥3500.
14. The PVDF-TrFE co-polymer of claim 13 , wherein p+q≤10,000.