the resin with lowered pdi according to the present invention comprises products provided by at least one reactive monomer , at least one initiator and at least one chain transfer reagent via polymerization in the present invention , the acrylate and derivatives thereof serving as reactive monomers can be acrylic acid , methyl acrylate , dimethylamino ethyl acrylate , diethylamino ethyl acrylate , ethyl acrylate , n - propyl acrylate , isopropyl acrylate , n - butyl acrylate , isobutyl acrylate , sec - butyl acrylate , t - butyl acrylate , hexyl acrylate , methacrylic acid alkyl ester , ( 1 , 6 - hexanediol di ( meth ) acrylate , neopentylglycol di ( meth ) acrylate , neopentylglycol adipate di ( meth ) acrylate ), neopentylglycol di ( meth ) acrylate hydroxypivalate , dicyclopentadienyl di ( meth ) acrylate , allylated cyclohexyl di ( meth ) acrylate , isocyanurate di ( meth ) acrylate , trimethylol propane tri ( meth ) acrylate , dipentaerythritol tri ( meth ) acrylate , propionic acid dipentaerythritol tri ( meth ) acrylate , pentaerythritol tri ( meth ) acrylate , tri ( acryloxyethyl ) isocyanurate , dipentaerythritol penta ( meth ) acrylate , dipentaerythritol hex ( meth ) acrylate or derivatives substituted optionally by at least one fluorine atom , alkyl , or alkyloxy group of the above . according to another aspect of the present invention , the acrylate and derivatives thereof can be acrylate monomers according to formula ( i ), as follows . wherein r 1 can be a hydrogen atom , a fluorine atom , a halogen atom , cyano group , saturated or unsaturated alkyl group , amino group , cycloalkyl group , heterocycloalkyl group , polycyclic alkyl group , aryl group , heteroaryl group , alkylaryl group , or arylalkyl group , wherein the saturated or unsaturated alkyl group can be straight or branched and has 1 to 12 carbon atoms . r 2 can be a hydrogen atom , saturated or unsaturated alkyl group , cycloalkyl group , heterocycloalkyl group , polycyclic alkyl group , adamantyl group , aryl group , heteroaryl group , alkylaryl group , or arylalkyl group , wherein the saturated or unsaturated alkyl group can be straight or branched and has 1 to 12 carbon atoms . in addition , at least one hydrogen atom bonded to the carbon atom of the acrylate monomers according to formula ( i ) can be substituted optionally by a fluorine atom , a halogen atom , cyano group , — r ″, co 2 h , — co 2 r ″, — r ″ co 2 h , — cor ″, — r ″ cn , — conh 2 , — conhr ″, — conr ″ 2 , — ocor ″, or — or ″, wherein r ″ can be a saturated or unsaturated alkyl group having 1 to 12 carbon atoms , thioalkyl group , alkynyloxy group , heterocycloalkyl group , alkoxy group , ester group , alkenyl group , alkynylene group , alkenyloxy group , heterocycloalkyl group , aryl group , alkylaryl group , heteroaryl group , arylalkyl group , or combinations thereof . moreover , at least one hydrogen atom bonded to the carbon atom of r ″ can be substituted optionally by a fluorine atom , or halogen atom , when r ″ has hydrogen atom bonded to the carbon . in the present invention , the norbornene and derivatives thereof serving as reactive monomers can be norbornene monomers according to formula ( ii ), as follows . wherein r 3 , r 4 , r 5 , and r 6 can be the same or different and a hydrogen atom , a fluorine atom , a halogen atom , cyano group , saturated or unsaturated alkyl group , amino group , cycloalkyl group , heterocycloalkyl group , polycyclic alkyl group , aryl group , heteroaryl group , alkylaryl group , or arylalkyl group , wherein the saturated or unsaturated alkyl group can be straight or branched and has 1 to 12 carbon atoms . in addition , at least one hydrogen atom bonded to the carbon atom of the norbornene monomers according to formula ( ii ) can be substituted optionally by a fluorine atom , a halogen atom , cyano group , — r ″, — co 2 h , — co 2 r ″, — r ″ co 2 h , — cor ″, — r ″ cn , — conh 2 , — conhr ″, — conr ″ 2 , — ocor ″, or — or ″, wherein the r ″ can be a saturated or unsaturated alkyl group having 1 to 12 carbon atoms , thioalkyl group , alkynyloxy group , heterocycloalkyl group , alkoxy group , ester group , alkenyl group , alkynylene group , alkenyloxy group , heterocycloalkyl group , aryl group , alkylaryl group , heteroaryl group , arylalkyl group , or combinations thereof . moreover , at least one hydrogen atom bonded to the carbon atom of the r ″ can be substituted optionally by a fluorine atom , or halogen atom , when r ″ has hydrogen atom bonded to the carbon . according to the present invention , the at least one initiator employed is an agent , such as peroxide initiators or azo initiators , which generates , upon activation , free radical species through decomposition , and can be 2 , 2 ′- azobis ( 2 - cyano - 2 - butane ), dimethyl 2 , 2 ′- azobis ( methyl isobutyrate ), 4 , 4 ′- azobis ( 4 - cyanopentanoic acid ), 4 , 4 ′- azobis ( 4 - cyanopentan - 1 - ol ), 1 , 1 ′- azobis ( cyclohexanecarbonitrile ), 2 -( t - butylazo )- 2 - cyanopropane , 2 , 2 ′- azobis [ 2 - methyl -( n )-( 1 , 1 )- bis ( hydroxymethyl )- 2 - hydroxyethyl ] propionamide , 2 , 2 ′- azobis [ 2 - methyl - n - hydroxyethyl )] propionamide , 2 , 2 ′- azobis ( n , n ′- dimethyleneisobutyramidine ) dihydrochloride , 2 , 2 ′- azobis ( 2 - amidinopropane ) dihydrochloride , 2 , 2 ′- azobis ( n , n ′- dimethyleneisobutyramine ), 2 , 2 ′- azobis ( 2 - methyl - n -[ 1 , 1 - bis ( hydroxymethyl )- 2 - hydroxyethyl ] propionamide , 2 , 2 ′- azobis ( 2 - methyl - n -[ 1 , 1 - bis ( hydroxymethyl ) ethyl ] propionamide ), 2 , 2 ′- azobis [ 2 - methyl - n -( 2 - hydroxyethyl ) propionamide ], 2 , 2 ′- azobis ( isobutyramide ) dihydrate , 2 , 2 ′- azobis ( 2 , 2 , 4 - trimethylpentane ), 2 , 2 ′- azobis ( 2 - methylpropane ), dilauroyl peroxide , tertiary amyl peroxides , tertiary amyl peroxydicarbonates , t - butyl peroxyacetate , t - butyl peroxybenzoate , t - butyl peroxyoctoate , t - butyl peroxyneodecanoate , t - butylperoxy isobutyrate , t - amyl peroxypivalate , t - butyl peroxypivalate , di - isopropyl peroxydicarbonate , dicyclohexyl peroxydicarbonate , dicumyl peroxide , dibenzoyl peroxide , potassium peroxydisulfate , ammonium peroxydisulfate , di - tert butyl peroxide , di - t - butyl hyponitrite , dicumyl hyponitrite or combinations thereof . in the present invention , the at least one chain transfer reagent can be reversible addition - fragmentation chain transfer reagent ( raft reagent ) according to the according to formula ( iii ), as follows . wherein z can be a hydrogen atom , a fluorine atom , a halogen atom , cyano group , saturated or unsaturated alkyl group , amino group , cycloalkyl group , heterocycloalkyl group , polycyclic alkyl group , aryl group , heteroaryl group , alkylaryl group , arylalkyl group , heteroalkylaryl group , — co 2 h , — co 2 r ″, — r ″ co 2 h , — cor ″, — conh 2 , — conhr ″, — conr ″ 2 , — ocor ″, — or ″, — sr ″, — nr ″ 2 , or — por ″ 2 , wherein r ″ can be a saturated or unsaturated alkyl group having 1 to 12 carbon atoms , thioalkyl group , alkynyloxy group , heterocycloalkyl group , alkoxy group , ester group , alkenyl group , alkynylene group , alkenyloxy group , heterocycloalkyl group , aryl group , alkylaryl group , heteroaryl group , arylalkyl group , or combinations thereof . furthermore , at least one hydrogen atom bonded to the carbon atom of z can be substituted optionally by a fluorine atom , or halogen atom , when z has hydrogen atom bonded to the carbon . r 7 can be a hydrogen atom , a fluorine atom , a halogen atom , cyano group , saturated or unsaturated alkyl group , amino group , cycloalkyl group , heterocycloalkyl group , polycyclic alkyl group , aryl group , heteroaryl group , alkylaryl group , or arylalkyl group , wherein the saturated or unsaturated alkyl group can be straight or branched and has 1 to 12 carbon atoms . in addition , at least one hydrogen atom bonded to the carbon atom of the raft reagent according to formula ( iii ) can be substituted optionally by a fluorine atom , a halogen atom , cyano group , — r ″, — co 2 h , — co 2 r ″, — r ″ co 2 h , — cor ″, — r ″ cn , — conh 2 , — conhr ″, — conr ″ 2 , — ocor ″, or — or ″, wherein r ″ can be a saturated or unsaturated alkyl group having 1 to 12 carbon atoms , thioalkyl group , alkynyloxy group , heterocycloalkyl group , alkoxy group , ester group , alkenyl group , alkynylene group , alkenyloxy group , heterocycloalkyl group , aryl group , alkylaryl group , heteroaryl group , arylalkyl group , or combinations thereof . moreover , at least one hydrogen atom bonded to the carbon atom of r ″ can be substituted optionally by a fluorine atom , or halogen atom , when r ″ has hydrogen atom bonded to the carbon . preferably , the raft reagent according to formula ( iii ) can be further suitable for use in the present invention through according to formula ( iv ), as follows . wherein z is defined as formula ( iii ); r 8 can be a saturated or unsaturated alkyl group having 1 to 12 carbon atoms , thioalkyl group , alkoxy group , alkenyl group , alkynylene group , alkenyloxy group , alkynyloxy group , or combinations thereof ; r 9 and r 10 are the same or different and defined as r 7 , wherein r 9 and r 10 may are jointly constructed of cycloalkyl group , heterocycloalkyl group , cycloalkenyl group , alkylaryl group , heteroaryl group , polycyclic alkyl group , or arylalkyl group ; x can be n or — ch ; and y can be o or s . in addition , at least one hydrogen atom bonded to the carbon atom of the raft reagent according to formula ( iv ) can be substituted optionally by a fluorine atom , a halogen atom , cyano group , — r ″, — co 2 h , — co 2 r ″, — r ″ co 2 h , — cor ″, — r ″ cn , — conh 2 , — conhr ″, — conr ″ 2 , — ocor ″, or — or ″, wherein r ″ can be a saturated or unsaturated alkyl group having 1 to 12 carbon atoms , thioalkyl group , alkynyloxy group , heterocycloalkyl group , alkoxy group , ester group , alkenyl group , alkynylene group , alkenyloxy group , heterocycloalkyl group , aryl group , alkylaryl group , heteroaryl group , arylalkyl group , or combinations thereof . moreover , at least one hydrogen atom bonded to the carbon atom of r ″ can be substituted optionally by a fluorine atom , or halogen atom , when r ″ has hydrogen atom bonded to the carbon . or combinations thereof , wherein at least one hydrogen atom bonded to the carbon atom of the above raft reagent can be substituted optionally by a fluorine atom , a halogen atom , cyano group , — r ″, — co 2 h , — co 2 r ″, — r ″ co 2 h , — cor ″, — r ″ cn , — conh 2 , — conhr ″, — conr ″ 2 , — ocor ″, or — or ″, wherein r ″ can be a saturated or unsaturated alkyl group having 1 to 12 carbon atoms , thioalkyl group , alkynyloxy group , heterocycloalkyl group , alkoxy group , ester group , alkenyl group , alkynylene group , alkenyloxy group , heterocycloalkyl group , aryl group , alkylaryl group , heteroaryl group , arylalkyl group , or combinations thereof . moreover , at least one hydrogen atom bonded to the carbon atom of r ″ can be substituted optionally by a fluorine atom , or halogen atom , when r ″ has hydrogen atom bonded to the carbon . the following embodiments are intended to clarify the invention more fully without limiting the scope of the claims , since numerous modifications and variations will be apparent to those skilled in this art . the following discloses the compound structures , names and symbols for the compounds in the embodiments and comparative embodiments of the present invention for better understanding . 0 . 5 g ( 3 . 42 mmol ) di - tert butyl peroxide ( dtbp ) was put into a polymerization bottle as an initiator , the bottle gas was displaced with nitrogen and 0 . 5 g ( 2 . 58 mmol ) nb3 and 0 . 5 g ( 1 . 34 mmol ) nb4 were added . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , and then the system was heated to 150 ° c . and reacted for 3 hours . next , the unreacted monomers were removed , and the residual was dissolved in toluene . after precipitation with pentane , 0 . 42 g of polymer product was obtained with average molecular weight of 16150 characterized by gel permeation chromatography ( gpc ) analysis , with pdi of 1 . 88 . 20 mg of azobisisobutyronitril ( aibn ) was put into a polymerization bottle as an initiator , the bottle gas was displaced with nitrogen . under nitrogen condition , 3 ml dehydrated ethyl acetate ( ea ) and monomers , 0 . 25 g ( 1 . 95 mmol ) tert - butyl acetate , 0 . 168 g ( 1 . 95 mmol ) methyl acrylate and 0 . 14 g ( 1 . 95 mmol ) acrylic acid , were added . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , and then the system was heated to 60 ° c . and reacted for 16 hours . after reaction and precipitation with pentane , 0 . 42 g of polymer product was obtained with average molecular weight of 45165 by gel permeation chromatography ( gpc ) analysis , with pdi of 2 . 07 . the above two comparative examples disclose conventional free radical polymerization . the monomers are polymerized by free radical initiators resulting in uncontrollable molecular weight of resin product . regardless of whether the monomer comprises unsaturated double bond acrylic monomers ( second comparative example ) or norbornene derivatives , the pdi range is larger , so the performance of the photoresist with the conventional polymerization resin as the main component decreases . the examples of the present invention describe the resin preparation . the polymerization not only uses free radical initiators to polymerize monomers , but also uses the chain transfer reagent to control the free radical polymerization . this polymerization controls the resin &# 39 ; s molecular weight precisely to tune resin characteristics , such that the low pdi resins of the present invention are obtained . 0 . 0045 g ( 0 . 027 mmol ) aibn , as an initiator , and 0 . 0125 g ( 0 . 036 mmol ) raft3 as a chain transfer reagent were put into a polymerization bottle , the bottle gas was displaced with nitrogen and 1 . 5 ml dehydrated toluene and monomers , 0 . 75 ml ( 5 . 75 mmol ) 85 % norbornene and 1 . 74 g ( 5 . 58 mmol ) nb1 , were added . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , the system was heated to 60 ° c . and reacted 48 hours . after reaction , the solvent was removed by vacuum evaporation and toluene was added . by precipitation with pentane , 0 . 1 g of polymer product was obtained with average molecular weight of 3610 by gel permeation chromatography ( gpc ) analysis , with pdi of 1 . 28 . 0 . 53 g ( 3 . 63 mmol ) dtbp , as an initiator , and 0 . 03 g ( 0 . 0873 mmol ) raft3 as a chain transfer reagent were put into a polymerization bottle , the bottle gas was displaced with nitrogen and 1 g of ( 3 . 65 mmol ) dehydrated toluene monomers was put into a polymerization bottle . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , the system was heated to 145 ° c . and reacted for 24 hours . after reaction , the solvent was removed and toluene was added . by precipitation with pentane , 0 . 47 g of polymer product was obtained with average molecular weight of 3699 by gel permeation chromatography ( gpc ) analysis , with pdi of 1 . 40 . 4 mg ( 0 . 024 mmol ) aibn , as an initiator , and 16 . 6 g ( 0 . 048 mmol ) raft3 as a chain transfer reagent were put into a polymerization bottle , the bottle gas was displaced with nitrogen . 3 ml dehydrated ethyl acetate and monomers , 0 . 25 g ( 1 . 95 mmol ) tert - butyl acetate , 0 . 168 g ( 1 . 95 mmol ) methyl acrylate and 0 . 14 g ( 1 . 95 mmol ) acrylic acid , were added under nitrogen . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , the system was heated to 60 ° c . and reacted for 16 hours . after reaction and precipitation with pentane , 0 . 45 g of polymer product was obtained with average molecular weight of 5756 by gel permeation chromatography ( gpc ) analysis , with pdi of 1 . 28 . 4 mg ( 0 . 024 mmol ) aibn , as an initiator , and 16 . 6 g ( 0 . 048 mmol ) raft3 as a chain transfer reagent were put into a polymerization bottle , the bottle gas was displaced with nitrogen and 3 ml dehydrated ethyl acetate and monomers , 0 . 5 g ( 3 . 9 mmol ) tert - butyl acetate , 0 . 168 g ( 1 . 95 mmol ) methyl acrylate and 0 . 14 g ( 1 . 95 mmol ) acrylic acid , were added . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , the system was heated to 60 ° c . and reacted for 16 hours . after reaction and precipitation with pentane , 0 . 7 g of polymer product was obtained with average molecular weight of 10146 by gel permeation chromatography ( gpc ) analysis , with pdi of 1 . 26 . 4 mg ( 0 . 024 mmol ) aibn , as an initiator , and 16 . 6 g ( 0 . 048 mmol ) raft3 as a chain transfer reagent were put into a polymerization bottle , the bottle gas was displaced with nitrogen and 3 ml dehydrated ethyl acetate under nitrogen and monomers , 0 . 225 g ( 0 . 96 mmol ) etada , 0 . 2 g ( 0 . 96 mmol ) nla and 0 . 107 g ( 0 . 48 mmol ) hada , were added . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , the system was heated to 60 ° c . and reacted for 72 hours . after reaction and precipitation with pentane , 0 . 46 g of polymer product was obtained with average molecular weight of 9000 by gel permeation chromatography ( gpc ) analysis , with pdi of 1 . 38 . 6 . 5 mg ( 0 . 04 mmol ) aibn , as an initiator , and 28 . 2 g ( 0 . 16 mmol ) raft2 as a chain transfer reagent were put into a polymerization bottle . the bottle gas was displaced with nitrogen and 3 ml dehydrated ethyl acetate and monomers , 0 . 225 g ( 0 . 96 mmol ) etada , 0 . 2 g ( 0 . 96 mmol ) nla and 0 . 107 g ( 0 . 48 mmol ) hada , were added under nitrogen . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , the system was heated to 60 ° c . and reacted for 24 hours . after reaction and precipitation with pentane , 0 . 42 g of polymer product was obtained with average molecular weight of 9300 by gel permeation chromatography ( gpc ) analysis , with pdi of 1 . 44 . 17 . 9 mg ( 0 . 109 mmol ) aibn , as an initiator , and 50 mg ( 0 . 226 mmol ) raft1 as a chain transfer reagent were put into a polymerization bottle , the bottle gas was displaced with nitrogen and 3 ml dehydrated toluene under nitrogen and monomers , 3 . 48 g ( 11 . 15 mmol ) nb1 and 1 ml ( 11 . 15 mmol ) methyl acrylate , were added . the above mixture were degassed with three freeze - pump - thaw cycles in the closed system to remove oxygen , the system was heated to 60 ° c . and reacted for 16 hours . after reaction , the solvent was removed and toluene was added . by precipitation with pentane , 0 . 1 g of polymer product was obtained with average molecular weight of 2409 by gel permeation chromatography ( gpc ) analysis , with pdi of 1 . 20 . the components , average molecular weight , and pdi of the resins according to the second comparative example , third example and fourth example are shown in table 1 . the polymerizations with chain transfer reagent ( as described in the third and fourth examples ) have lower pdi and molecular average weight than those without ( as described in the second comparative example ). therefore , the resin with lowered pdi of the present invention comprises monomers polymerized by free radicals , further using the chain transfer reagent to control the free radical polymerization , to obtain resin with lowered pdi . in addition , due to the chain transfer reagent addition , the resin with lowered pdi preparation of the present invention can be used for polymerization of norbornene monomers , and copolymerization of norbornene monomers and acrylate monomers . furthermore , the resin with lowered pdi of the present invention can be tuned easily to improve photoresist performance . while the invention has been described by way of example and in terms of the preferred examples , it is to be understood that the invention is not limited to the disclosed examples . to the contrary , it is intended to cover various modifications and similar arrangements ( as would be apparent to those skilled in the art ). therefore , the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements .