E. I. du Pont de Nemours & Co. announced yesterday that Richard E. Heckert will succeed Edward G. Jefferson as chairman next year, a change that is intended to assure continuity as the nation's largest chemical company makes a difficult pivot into new technologies.

Heckert, 61, a member of Du Pont's top management for a dozen years, will become chairman and chief executive on May 5, when Jefferson, who has been in the post since 1981, retires. Heckert was promoted from vice chairman to deputy chairman yesterday.

Taking Heckert's place as vice chairman is one of Du Pont's fastest-rising executives, 51-year-old Edgar S. Woolard Jr. As executive vice president before his promotion yesterday, Woolard had guided the company's deepening push into biotechnology, agricultural chemicals and electronics products -- the "keys to our future," Jefferson said yesterday.

Woolard will be responsible for all of Du Pont's operations excluding Conoco, the oil and gas company Du Pont acquired in 1981. Du Pont vice chairman Ralph E. Bailey continues to direct Conoco.

The challenge Heckert and Woolard face is managing Du Pont's continuing transition from its historic base in chemicals, fibers and textiles products into an array of newer technologies. Scrapping its traditional label of a chemical company, Du Pont now calls itself a "discovery" company. Its research and development spending exceeded $1.1 billion last year, up 14 percent from 1983, and this year's budget is higher still, one-quarter of it spent on health and plant sciences.

In the past few years, Du Pont has closed down some 20 businesses that no longer met its growth goals, and today more than half of its businesses are in high-tech specialty products rather than bulk commodities.

But these efforts to reduce costs and shift into faster-growing markets have been made as the company has felt the impact of the high dollar and intense foreign competition on its businesses. This year has become a struggle for Du Pont, which reported a $268 million profit on sales of $8.5 billion for the second quarter of 1985, compared to a $437 million profit on sales of $9.1 billion for the same period in 1984.

An example of the shift in direction at Du Pont is Heckert's assignment to strengthen Du Pont's marketing efforts. The goal, Jefferson and Heckert said, is to build a stronger bridge between Du Pont's laboratories and its customers, to tailor research much more closely to customer needs and product development opportunities.

A decade ago, Heckert was a familiar figure in congressional corridors -- he led the chemical industry's lobbying efforts at a time when the industry was under intense fire from critics over work place safety and toxic waste disposal issues.

Today, what Heckert wants from Washington is a breakthrough on the federal budget impasse. Like Jefferson, he blames federal economic policies for helping boost the dollar to ruinous levels for American industry.

"The dollar is such a serious problem that something will have to give," Heckert said yesterday. "Either we'll do the things that will bring it down at a reasonable pace, or at some point it will come down with a thud. The question is a hard landing or a soft landing."

"My concern is that the whole American industrial infrastructure is being torn up by this very strong dollar and this dedication to uninhibited trade . . . .

"We'd like to get more help from government," on both the budget and trade fronts, Heckert said. "If they don't get their act together, we have a real challenge."

Characteristically, Du Pont chose as its next chairman a former research scientist-turned-executive who has spent his working life at the company. Heckert got his undergraduate degree at Miami University of Ohio.

Heckert, who got a PhD in chemistry from the University of Illinois, joined Du Pont in 1949 and moved into research management, working with cellophane and other products.

He lives on a farm outside Wilmington, Del., which is equipped with a landing pad for rapid transportation aboard company helicopters to Washington and other destinations. At 6-feet 3-inches tall and 235 pounds, Heckert enjoys a reputation as a long-hitting, low-handicap golfer, a sport that "helps keep life worth living," he said.

Woolard, an industrial engineer educated at North Carolina State University, joined Du Pont after graduation in 1957 and moved up the management ranks to become head of Du Pont's textile fibers business in 1981.

"He has excellent business instincts," said Jefferson. "And I think he is able to do the tough things in a way that plays well. Where difficult changes have to be taken, he knows how to go about it and retain an organization with high morale.