Poly(meth)acrylamide-based copolymers with carboxyl-terminated pendant chains

A packaging solution, which is an aqueous solution comprising at least one buffering agent for maintaining a pH of from about 6.0 to about 8.5 and from about 0.01% to about 2% by weight of a water-soluble and thermally-crosslinkable hydrophilic polymeric material, wherein the packaging solution has a tonicity of from about 200 to about 450 milliosmol (mOsm) and a viscosity of from about 1 centipoise to about 20 centipoises at 25° C., wherein the water-soluble thermally-crosslinkable polymeric material comprises:

• (a) one or more first polymer chain of an azetidinium-containing polymer having azetidinium groups;
• (b) one or more second polymer chains of a poly(meth)acrylamide-based copolymer, wherein each second polymer chain is covalently attached to one of said one or more first polymer chains via at least one linkage formed between one azetidinium group of the azetidinium-containing polymer and one reactive pendant chain of the poly(meth)acrylamide-based copolymer, wherein the poly(meth)acrylamide copolymer comprises
• (i) first repeating units of at least one (meth)acrylamide monomer selected from the group consisting of (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-2-hydroxyethyl (meth)acrylamide, N-3-hydroxypropyl (meth)acrylamide, N-2-hydroxypropyl (meth)acrylamide, N-4-hydroxybutyl (meth)acrylamide, N-5-hydroxypentyl (meth)acrylamide, N-6-hydroxyhexyl (meth)acrylamide, N-(2,3-dihydroxypropyl) (meth)acrylamide, N,N-bis(2-hydroxyethyl) (meth)acrylamide, N-tris(hydroxymethyl) methyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, and combinations thereof, and
• (ii) second repeating units each of which is an acrylic repeating unit of any one of formula (1) to (5)
• in which Ro is hydrogen or methyl, X0 and X1 independent of each other are —O— or —NRn— in which Rn is hydrogen or a C1-C4 alkyl group, L1 is a C1-C4 alkylene divalent radical, L2 and L4 independent of each other are a C2-C4 alkylene divalent radical having 0 or 1 hydroxyl group, L3 is —CH2—CHOH—CH2—, t1 is an integer of 2 to 25, t2 is an integer of 2 to 4, and t3 is 0 or 1, wherein the poly(meth)acrylamide-based copolymer comprises at least 60% by mole of all (meth)acrylamide repeating units relative to all repeating units of the poly(meth)acrylamide-based copolymer.