John Whybrow, the Chairman of AZ Electronic Materials, which on Tuesday tanked after it issued a warning on full year revenue, has shown his faith in the chemicals company by enlarging his shareholding. Whybrow acquired 40,000 shares at 254p each for a total trade value of £101,600, taking his stake in the company to 118,541 shares. Geoff Wild, the group's Chief Executive Officer, also made a significant purchase, buying 40,000 shares at 268p each. The £107,200 purchase takes his holding to 885,749.A number of other directors also gave the group their backing with purchases of various sizes. The company reported a 2.0% year-on-year decline in revenue to $19.9m for the three months to April 8th, following lower-than-expected sales in its IC Materials division. The company blamed weak performance and an unfavourable product mix in IC Materials, which includes products for use in integrated circuits and devices. Revenue in the division fell 7.0% year-on-year to $123.3m. As a result, the group's EBITDA (earnings before interest, tax, depreciation and amortisation) margin for the three month period was lower than normal, and will be for the year as a whole, it warned. Group revenue for the full year will be around the same levels as last year, the company added. Having lost around 30% of its value on Tuesday, the stock regained 15% the following morning, boosted in part by a rating upgrade from broker UBS. Top Director BuysCentamin (DI) (CEY) Director name: Mr Josef El-RaghyAmount purchased: 500,000 @ 47.80p Value: £239,000AZ Electronic Materials SA (DI) (AZEM) Director name: Mr Geoff WildAmount purchased: 40,000 @ 268.00p Value: £107,200AZ Electronic Materials SA (DI) (AZEM) Director name: Mr John WhybrowAmount purchased: 40,000 @ 254.00p Value: £101,600Synety Group (SNTY) Director name: Mr Simon CleaverAmount purchased: 40,000 @ 125.00p Value: £50,000AZ Electronic Materials SA (DI) (AZEM) Director name: Mr Andrew AllnerAmount purchased: 10,000 @ 255.00p Value: £25,500Verona Pharma (VRP) Director name: Mr Stuart BottomlyAmount purchased: 1,000,000 @ 2.35p Value: £23,500Mission Marketing Group (TMMG) Director name: Mr Chris GoodwinAmount purchased: 60,000 @ 34.00p Value: £20,400Cenkos Securities (CNKS) Director name: Mr Anthony HotsonAmount purchased: 20,000 @ 87.80p Value: £17,560Port Erin Biopharma Investments Ltd (PEBI) Director name: Mr James (Jim) MellonAmount purchased: 200,000 @ 7.50p Value: £15,000Synety Group (SNTY) Director name: Mr Simon CleaverAmount purchased: 10,000 @ 124.80p Value: £12,480Top Director SellsTelecity Group (TCY) Director name: Mr Brian McArthur MuscroftAmount sold: 98,789 @ 888.00p Value: £877,246Close Brothers Group (CBG) Director name: Mr Stephen R HodgesAmount sold: 76,383 @ 1,016.48p Value: £776,418Berendsen (BRSN) Director name: Mr Peter VentressAmount sold: 61,310 @ 782.80p Value: £479,935Spirax-Sarco Engineering (SPX) Director name: Mr Mark E. VernonAmount sold: 18,362 @ 2,608.78p Value: £479,024Amlin (AML) Director name: Mr Richard A HextallAmount sold: 72,533 @ 423.49p Value: £307,170Tarsus Group (TRS) Director name: Mr Douglas EmslieAmount sold: 86,449 @ 230.00p Value: £198,833National Express Group (NEX) Director name: Mr Dean K FinchAmount sold: 69,571 @ 195.89p Value: £136,283Tarsus Group (TRS) Director name: Mr Neville BuchAmount sold: 43,225 @ 230.00p Value: £99,418Tarsus Group (TRS) Director name: Mr Roger PellowAmount sold: 23,084 @ 230.00p Value: £53,093NR