Organically modified aerogels, processes for their preparation by surface modification of the aqueous gel, without prior solvent exchange, and subsequent drying, and thier use

The process as claimed in at least one of the preceding claims, wherein the hydrogel obtained in step a) is aged before being surface-modified in step b).

The process according to at least one of the preceding claims, wherein the hydrogel obtained in step b) is subjected to surface silylation.

The process as claimed in at least one of the preceding claims, wherein at least one acid and/or base is introduced as initial charge in the hydrogel before surface modification.

The process as claimed in at least one of the preceding claims, wherein the hydrogel is introduced as initial charge in the silylating agent or agents, and then at least one acid and/or base is added.

The process as claimed in at least one of the preceding claims, wherein the agent for surface modification is generated shortly before and/or during the surface modification, preferably by means of an acid.

The process as claimed in at least one of the preceding claims, wherein the surface modification is accelerated by means of a catalyst.

The process as claimed in at least one of the preceding claims, wherein at least one carrier gas or carrier gas stream is used in step b) in addition to the agent for surface modification.

The process as claimed in at least one of the preceding claims, wherein some of the water in the pores of the hydrogel reacts with the surface modification agent used to form a water-insoluble compound.

The process as claimed in at least one of the preceding claims, wherein the outer surface of the hydrogel is dried prior to surface modification.

The process as claimed in at least one of the preceding claims, wherein the surface-modified gel is washed with a protic or aprotic solvent prior to step c).

The process as claimed in at least one of the preceding claims, wherein the surface-modified gel is washed with a silylating agent prior to step c).

The process as claimed in at least one of the preceding claims, wherein the surface-modified gel is subjected to subcritical drying in step c).

The process as claimed in one of the preceding claims, wherein surface modification is carried out in the presence of additives in the hydrogel.

An aerogel which is free from Si—OR groups.

An aerogel the degree of coverage of whose internal surface with organic surface groups which have been applied by surface modification, preferably surface silylation, is at least 90% of the theoretically possible value.

An aerogel which has a thermal conductivity of <12 mW/mK.

A process for producing an organically modified lyogel, which comprises

• a) introducing a hydrogel as initial charge and
• b) subjecting the hydrogel obtained in step a) to surface modification.

A lyogel which is free from Si—OR groups.

A lyogel the degree of coverage of whose internal surface with organic surface groups which have been applied by surface modification, preferably surface silylation, is at least 90% of the theoretically possible value.