NANOMATERIALS

1 . A compound of Formula (IIIA):

or a pharmaceutically acceptable salt thereof, wherein:

R 1 is a saturated or unsaturated, straight or branched C 6 -C 20 hydrocarbon chain;

L 4 is independently a bivalent saturated or unsaturated, straight or branched C 1 -C 6 hydrocarbon chain;

each A 1 and A 2 is optionally substituted C 1 -C 9 aliphatic,

Y 1 is —C(O)—;

Y 2 is a bivalent saturated, straight or branched C 1 -C 3 hydrocarbon chain;

Y 3 is a saturated or unsaturated, straight or branched C 1 -C 8 hydrocarbon chain;

X 1 is a covalent bond, —O—, or —NR—;

each R is independently hydrogen or an optionally substituted C 1 -C 6 aliphatic group and —X 2 —X 3 is selected from:

2 .- 16 . (canceled)

17 . The compound of claim 1 , wherein R 1 is

18 .- 28 . (canceled)

29 . The compound of claim 1 , wherein each of A 1 and A 2 are independently selected from:

30 .- 34 . (canceled)

35 . The compound of claim 1 , wherein X 1 is a covalent bond.

36 . The compound of claim 1 , wherein X 1 is —O—.

37 . The compound of claim 1 , wherein X 1 is —NR—.

38 . The compound of claim 1 , wherein X 1 is —NH—.

39 .- 56 . (canceled)

57 . The compound of claim 1 , wherein the compound is selected from the group consisting of:

or a pharmaceutically acceptable salt thereof.

58 . A lipid nanoparticle (LNP) comprising an ionizable lipid that is a compound according to claim 1 .

59 . A lipid nanoparticle (LNP) comprising:

an ionizable lipid that is a compound according to claim 1 ;

a phospholipid;

a cholesterol; and

a polyethylene glycol lipid.

60 . The LNP of claim 58 , further comprising a therapeutic and/or prophylactic agent.

61 . The LNP of claim 60 , wherein the therapeutic and/or prophylactic agent is or comprises one or more nucleic acids.

62 . The LNP of claim 61 , wherein the one or more nucleic acids is or comprises RNA.

63 . The LNP of claim 61 , wherein the one or more nucleic acids is or comprises DNA.

64 .- 66 . (canceled)

67 . A pharmaceutical composition comprising a LNP of claim 58 and a pharmaceutically acceptable excipient.

68 .- 77 . (canceled)