Filtration membranes
Polymeric membranes are modified via SIS to promote membrane resilience, prolong membrane lifetime, and mitigate fouling. Modified membranes include an inorganic material within an outer portion of the modified membrane and a polymeric core that remains unmodified by the inorganic material. The polymer may be removed leaving an inorganic material patterned from an initial unmodified polymeric membrane.
1. A method for forming a membrane with inorganic features comprising:
(a) exposing a polymer membrane, which comprises a polyvinylidene fluoride polymer substrate, with a first precursor, comprising trimethyl aluminum (TMA), wherein exposing the first precursor comprises exposing the TMA in at least five exposure pulses for at least 5 continuous minutes of dwell time with a first precursor partial pressure of 1 torr to form by a first reaction a first layer within a bulk of the polymer substrate;
(b) purging excess first precursor and first reaction by-product;
(c) reacting the first layer with a second precursor within the bulk of the polymer substrate by a second reaction; and
(d) purging excess second precursor and second reaction by-product,
wherein steps (a) to (d) constitute one cycle and steps (a) to (d) are repeated 0 to 4 times, and
forming the membrane with inorganic features comprising an inorganic shell within the polymer substrate.
2. The method of claim 1 , wherein each of the at least five exposure pulses is 0.04 seconds and wherein 20 seconds separates each exposure pulse.
3. The method of claim 1 , wherein the second precursor is an oxidizer.
4. The method of claim 1 , wherein the second precursor comprises water.
5. The method of claim 1 , further comprising treating the polymer substrate with a hydrophilic enhancer prior to exposing the first precursor to the polymer substrate.
6. The method of claim 1 , further comprising removing the polymer substrate from the membrane so that the membrane comprises the inorganic shell.
7. The method of claim 6 , wherein removing the polymer substrate comprises a process selected from thermal treatment, plasma treatment, or chemical treatment.
8. The method of claim 1 , comprising repeating steps (a) to (d) 0 to 4 times, wherein the inorganic shell is the outer 10% of the membrane.
9. The method of claim 1 , further comprising, during one or both of reacting the polymer substrate with the first precursor and reacting the first layer with the second precursor, providing a backflow of inert backflow gas.
10. A method for forming a membrane with inorganic features comprising:
(a) exposing a polymer membrane, which comprises a polymer substrate, with a first precursor, comprising trimethyl aluminum (TMA), wherein exposing the first precursor comprises exposing the TMA in at least five exposure pulses for at least 5 continuous minutes of dwell time with a first precursor partial pressure of 1 torr to form by a first reaction a first layer within a bulk of the polymer substrate;
(b) purging excess first precursor and first reaction by-product;
(c) reacting, by a second reaction, the first layer with a second precursor within the bulk of the polymer substrate; and
(d) purging excess second precursor and second reaction by-product,
wherein steps (a) to (d) constitute one cycle and steps (a) to (d) are repeated 0 to 4 times,
forming the membrane with inorganic features comprising an inorganic shell within the polymer substrate.