Those to have their shares suspended include Azure Holdings, formerly the scandal-hit Room Service, and Capricorn Resources, an investment firm formerly chaired by the mining entrepreneur Phil Edmonds.
Another, Gasol, is headed by Haresh Kanabar, a cash-shell specialist holding senior jobs at several.
Mr Kanabar is involved in Black Raven Properties, which avoided suspension after a land deal in Portugal last week, and Indian Outsourcing Services, which raised £3m and is thought on the brink on unveiling an acquisition.
The 38 so-called "cash shells", each with less than £3m in the bank but still valued at a total of about £54m, were all set up and floated with the intention of buying other businesses to run.
The London Stock Exchange, which runs AIM, is concerned that many of the glut of cash shells joining the junior market sit there for too long without using any of their cash. The share prices of the smallest companies were too easy to manipulate, it said.
They are difficult to value and some investors were buying in simply to take advantage of tax breaks.
A spokesman for the LSE said: "Well-capitalised cash shells that have a clear investment strategy have a valid home on AIM. But small, uninvested cash shells present an unacceptably high reputational risk for the market and are not suitable to be quoted on it."
In March, the LSE warned that it wanted to stem that steady stream of cash shells by giving them only a short window in which to do a deal and forcing any company coming to AIM after 1 April to raise at least £3m.
Those sitting on at least that must now hold a meeting of investors every year to vote on an investment strategy until a deal is done.
Companies with less than £1m were given a year to make an acquisition or face suspension.
The number of companies to be frozen would have been much higher, it was said, but for a flurry of about 15 deals in the past fortnight to beat the deadline. About 75 of the 1,400-odd companies now trading on the junior market are thought to be cash shells.
Suspended companies have six months in which to do a deal or be dropped from AIM altogether.
Suspension is likely in itself to make any acquisition tougher, as managers of target companies take advantage of the looming deadline to push for better terms. For those that are delisted, the most attractive option is likely to be the lightly regulated Ofex exchange.
Moving to Ofex will hit a company's market value, but would save shareholders from finding themselves stranded in a wholly private company with less chance of selling on their stakes.Reuse content