Thermally degradable polymeric fibers
A microvascular system includes a solid polymeric matrix and a woven structure in the matrix. The woven structure includes a plurality of fibers, and a plurality of microfluidic channels, where at least a portion of the microfluidic channels are interconnected. The microvascular system may be made by forming a composite that includes a solid polymeric matrix and a plurality of sacrificial fibers in the matrix, heating the composite to a temperature of from 100 to 250° C., maintaining the composite at a temperature of from 100 to 250° C. for a time sufficient to form degradants from the sacrificial fibers, and removing the degradants from the composite. The sacrificial fibers may include a polymeric fiber matrix including a poly(hydroxyalkanoate) and a metal selected from the group consisting of an alkali earth metal and a transition metal, in the fiber matrix, where the concentration of the metal in the fiber matrix is at least 0.1 wt %.
1. A method of making a microvascular system, comprising:
forming a composite comprising:
a solid polymeric matrix, and
a plurality of sacrificial fibers having a degradation temperature of from 180 to 250° C. in the polymeric matrix;
where the sacrificial fibers comprise a poly(hydroxyalkanoate) and at least 0.1 wt % of a metal compound selected from the group consisting of a tin salt of a mono- or di-carboxylic acid, and scandium triflate (Sc(OTf) 3 );
heating the composite to a temperature of from 100 to 250° C.;
maintaining the composite at a temperature of from 180 to 250° C. for a time sufficient to form degradants from the sacrificial fibers; and
removing the degradants from the composite to provide the microvascular system.
2. The method of claim 1 , where the forming of the composite comprises:
contacting the sacrificial fibers with a non-solid polymeric matrix precursor; and
solidifying the polymeric matrix precursor to form the composite comprising the sacrificial fibers in the solid polymeric matrix.
3. A method of making a microvascular system, comprising:
forming a composite comprising:
a solid polymeric matrix, and
a woven structure in the polymeric matrix, the woven structure comprising a plurality of reinforcing fibers, and a plurality of sacrificial fibers having a degradation temperature of from 180 to 250° C.;
where the sacrificial fibers comprise a poly(hydroxyalkanoate) and at least 0.1 wt % of a metal compound selected from the group consisting of a tin salt of a mono- or di-carboxylic acid, and scandium triflate (Sc(OTf) 3 );
heating the composite to a temperature of from 100 to 250° C.;
maintaining the composite at a temperature of from 180 to 250° C. for a time sufficient to form degradants from the sacrificial fibers; and
removing the degradants from the composite to provide the microvascular system.
4. The method of claim 3 , where the woven structure comprises warp threads and weft threads in two dimensions, and at least a portion of the sacrificial fibers are present as weft threads.
5. The method of claim 3 , where the woven structure comprises warp threads, weft threads and Z-threads in three dimensions, and at least a portion of the sacrificial fibers are present as weft threads or Z-threads.
6. The method of claim 3 , where the forming of the composite comprises:
contacting the sacrificial fibers with a non-solid polymeric matrix precursor; and
solidifying the polymeric matrix precursor to form the composite comprising the woven structure in the solid polymeric matrix.
7. The method of claim 3 , where at least a portion of the microvascular system comprises interconnected microfluidic channels.
8. The method of claim 1 , where the sacrificial fibers have a degradation temperature of at most 220° C.
9. The method of claim 1 , where the sacrificial fibers have a degradation temperature of at most 180° C.
10. A method of making a degradable polymeric fiber, comprising:
combining:
a fiber comprising a poly(hydroxyalkanoate), and
a composition comprising a fluorinated fluid and a metal compound selected from the group consisting of a tin salt of a mono- or di-carboxylic acid, and scandium triflate (Sc(OTf) 3 );
maintaining the fiber and the composition together at a suitable temperature and for a time sufficient to provide a concentration of the metal compound in the fiber of at least 0.1 wt %; and
separating the fiber from the fluorinated fluid to form the degradable polymeric fiber having a degradation temperature of from 180 to 250° C.
11. The method of claim 10 , where the poly(hydroxyalkanoate) comprises poly(lactic acid) (PLA).
12. The method of claim 10 , where the tin salt of a mono- or di-carboxylic acid comprises tin(II) acetate, tin(II) oxalate or tin(II) octoate.
13. The method of claim 10 , further comprising cold-drawing the degradable polymeric fiber.
14. The method of claim 1 , where the metal compound has been incorporated in the sacrificial fibers by a process comprising infusion, liquid spinning, or melt spinning.
15. The method of claim 3 , where the metal compound has been incorporated in the sacrificial fibers by a process comprising infusion, liquid spinning, or melt spinning.
16. The method of claim 1 , where the metal compound has a concentration of at least 1 wt %.
17. A microvascular system prepared by the method of claim 1 .
18. A microvascular system prepared by the method of claim 3 .
19. The method of claim 1 , where the poly(hydroxyalkanoate) comprises poly(lactic acid) (PLA).
20. The method of claim 3 , where the poly(hydroxyalkanoate) comprises poly(lactic acid) (PLA).