block copolymers self - assemble 
 on the 10100 nm length scale 
 and are attractive materials to structure direct inorganic components 
 into materials with mesoscale features . one route to such materials involves the use of block copolymers 
 as sacrificial templates . this strategy 
 involves selective degradation of one polymer block to form ordered 
 mesoporous structures and deposition of inorganic materials into the 
 open mesopores . in particular , this approach has been used for the 
 synthesis of inorganic network structures for metals and metal oxides . the incorporation of two distinct inorganic components into 
 the 
 same block copolymer template enables the fabrication of previously 
 unknown classes of complex , multifunctional materials for a wide range 
 of potential applications . thomas and co - workers reported coassembly of a binary mixture 
 of sio2 and au nanocrystals of different sizes with a lamellar - forming 
 diblock copolymer . the segregation of the nanocrystals to different 
 areas within the structure was based primarily on entropic contributions . alternatively , li et al . demonstrated synthesis 
 of ordered metal networks from coassembly of abc triblock terpolymers 
 and a mixture of pt and au nanoparticles , where the pt and au nanoparticles 
 localized in specific areas within the structure based on ligand chemistry . stamm and co - workers reported orthogonal deposition 
 of two different metal nanoparticles into different domains of block 
 copolymer thin films . this process was achieved through a combination 
 of coassembly with the first polymer domain and nanoparticle deposition 
 using adsorption to the second polymer domain in a separate processing 
 step . furthermore , in no previous 
 examples have two inorganic components been orthogonally deposited 
 into two different domains of bulk block copolymer films via an etching 
 and backfilling mechanism . using a templating approach would require 
 block copolymers that can be orthogonally degraded and backfilled . 
 with orthogonality here we mean that two of the three blocks of the 
 abc terpolymer can be degraded and backfilled independently from one 
 another , without interference from the other . abc triblock terpolymers 
 where two different blocks could be removed 
 orthogonally would enable fabrication of composites constituted by 
 two distinct inorganic materials in two different domains separated 
 by a third polymer domain . in the case of triply periodic network 
 structures , two separate networks could be sequentially degraded and 
 the resulting porous structures backfilled , providing access to triply 
 periodic composite structures . abc triblock terpolymers and their 
 composites benefit from the formation of triply periodic network morphologies 
 over larger composition regions than diblock copolymers . in addition , their use opens potential pathways to remove the remaining 
 third block after orthogonal backfilling to produce porosity in the 
 final composite structure . to that end , we synthesized a series 
 of new triblock terpolymers 
 of polyisoprene - block - polystyrene - block - poly(propylene carbonate ) ( pi - b - ps - b - ppc ) that self - assemble into cocontinuous network morphologies including 
 the q alternating gyroid , o orthorhombic 
 network , and q core  shell double gyroid morphologies 
 and have orthogonal degradability of the polyisoprene ( pi ) and poly(propylene 
 carbonate ) ( ppc ) end blocks in bulk films . the pi block was degraded 
 using irradiation with uv light , and the ppc block was labile in basic 
 solutions . via electroless plating and seeded growth deposition au , 
 ni , and cu metals were deposited into the mesoporous channels produced 
 by degradation of either the pi or ppc blocks , as evidenced by transmission 
 electron microscopy ( tem ) . as a proof of principle , we report the 
 orthogonal deposition of au and cu metal into a single polymer template 
 through sequential degradation and backfilling of the pi and ppc blocks , 
 respectively . incorporation of au and cu metal was characterized using 
 high - angle annular dark field scanning transmission electron microscopy 
 ( haadf stem ) and haadf stem tomography . the polystyrene ( ps ) block 
 could be removed from the final composite structures by pyrolysis 
 or dissolution to remove any remaining organic material . salen co(iii ) complex ( 1 ) was prepared according to 
 previous literature procedures . pi - b - ps - oh ( supporting information ) , 1 , and [ ppn]cl were added to a 150 ml fischer  porter 
 bottle in a glovebox . propylene oxide was added to the reactor to 
 produce the following concentrations : [ pi - b - ps - oh ] 
 = 14 mm ,   = 1.4 mm , [ ppn]cl = 1.4 mm . the reactor 
 was sealed in the glovebox , removed and pressurized to 6.8 atm with 
 co2 . the 
 length of the poly(propylene carbonate ) ( ppc ) block produced is proportional 
 to the reaction time . after the desired chain length is achieved , 
 the reactor was depressurized , and the polymerization was quenched 
 by adding methanol . a small amount of ppc homopolymer is produced 
 during the rapid chain - shuttling polymerization of ppc due to initiation 
 from the pentafluorobenzoate and chloride anions on the catalyst and 
 cocatalyst , respectively . the pi - b - ps - b - ppc triblock terpolymer was purified 
 by dissolving precipitated polymer in minimal amounts of thf , and 
 adding methanol to precipitate the polymer from solution . the dissolution 
 and precipitation process was repeated a total of three times to remove 
 residual 1 , [ ppn]cl salt , and ppc homopolymer from the 
 pi - b - ps - b - ppc . polymer overlayers were removed from 
 the film surfaces using air 
 plasma in a harrick plasma cleaner . films were plasma cleaned for 
 10 min and removed from the plasma cleaner and turned over a total 
 of four times for a total of 40 min of plasma treatment . uv 
 degradation was performed using a uvp el - series 8w lamp with 
 a wavelength of 302 nm . plasma - cleaned polymer films were irradiated 
 with 302 nm uv light to selectively degrade the pi block . the polymer 
 films were placed at a distance of 3 in . under an 8w 302 nm uv lamp 
 for 72 h. the polymer films were soaked in methanol for 48 h to remove 
 any small molecule degradation products . the uv treatment cross - links 
 the ps block slightly , which appears as a broadening of the molar 
 mass distribution of the polymers from dissolved films by gpc after 
 uv treatment . cross - linking of the ps to the point of insolubility 
 was observed only for the top surface of the polymer film ; the amount 
 of insoluble material was too small to be quantified by mass . plasma - cleaned 
 polymer films were soaked in a solution of 1.25 
 m naoh : methanol at a 1:2 ratio by volume for 60 h to selectively degrade 
 the ppc block . small - molecule degradation products were removed by 
 soaking the degraded films in methanol for 48 h. no adverse effects 
 on the ps or pi blocks were observed after degradation with naoh . rather 
 than the degradation sequence pi first and then ppc , the degradation 
 order can be reversed , degrading the ppc block first and then the 
 pi block ( i.e. , naoh first , followed by uv degradation ) . electroless 
 and seeded growth deposition procedures can be found 
 in the supporting information . we synthesized a series of new orthogonally degradable 
 pi - b - ps - b - ppc triblock terpolymers 
 using a combination of anionic and rapid chain - shuttling polymerization 
 ( figure 1a ) . in rapid chain - shuttling 
 polymerization ( also called immortal polymerization ) , the polymerization 
 reaction is catalyzed using a lewis acid catalyst in the presence 
 of chain - shuttling agents ( csas ) such as alcohols . when the rate of 
 chain - shuttling between csas is faster than the rate of monomer incorporation , 
 controlled molar masses and narrow molar mass distributions result . rapid chain - shuttling polymerization is the catalytic variant of 
 a living polymerization , requiring substoichiometric amounts of catalyst 
 relative to the number of chains produced in the polymerization , rather 
 than stoichiometric amounts of an initiator . polyisoprene - b - polystyrene diblock copolymers were synthesized using 
 the sequential living anionic polymerization of isoprene and styrene 
 and terminated with a hydroxyl group ( pi - b - ps - oh ) 
 to act as macro - chain - shuttling agents . poly(propylene carbonate ) was grown off of the macro - chain - shuttling 
 agents via the alternating copolymerization of propylene oxide and 
 co2 by a salen co(iii ) complex ( 1 ) and a bis(triphenylphosphine)iminium 
 chloride ( [ ppn]cl ) cocatalyst . we chose a polycarbonate block to potentially tune the block chemistry 
 through functionalized terminal epoxides and for potential resistance 
 of the polycarbonate block to oxidative conditions . we designed the 
 new pi - b - ps - b - ppc triblock terpolymer 
 to have orthogonal degradability and found the pi and ppc blocks could 
 be removed via irradiation with 302 nm uv light and naoh , respectively 
 ( figure 1b ) . synthesis and orthogonal degradation schemes 
 of abc triblock terpolymer 
 pi - b - ps - b - ppc . ( a ) synthesis of 
 pi - b - ps - oh using anionic polymerization and synthesis 
 of pi - b - ps - b - ppc triblock terpolymers 
 from the parent pi - b - ps - oh diblock copolymer using 
 rapid chain - shuttling polymerization of propylene oxide and co2 using 1 . ( b ) schematic illustrating orthogonal 
 degradation of pi and ppc blocks of pi - b - ps - b - ppc from a q core we mapped out sections of the pi - b - ps - b - ppc phase space to locate compositions where 
 the triblock terpolymers self - assembled into cocontinuous network 
 structures such as the cubic q alternating gyroid , the 
 orthorhombic o network , and the cubic q core the structure is made 
 up of two chemically distinct minority gyroid networks of pi and ppc , 
 respectively , embedded in a matrix of the ps block . similarly , in the o network structure , the 
 structure consists of two chemically distinct orthorhombic continuous 
 minority networks of pi and ppc , respectively , embedded in a matrix 
 of ps . finally , in 
 the q core shell double gyroid the structure 
 is made up of two gyroid minority networks of ppc coated with a shell 
 of ps . in this case different pi - b - ps - b - ppc triblock terpolymers and their compositions for which we identified 
 these self - assembled network structures are summarized in table 1 . pi - b - ps - b - ppc 
 terpolymers from table 1 will be referred to 
 as pi - b - ps - b - ppc - x , where x denotes 
 table 1 entry number . determined by h nmr 
 spectroscopy in cdcl3 ( 400 mhz ; n = 8 , d1 = 10s , pw = 45 ) . subscripts denote number 
 of monomers in each block determined by gpc in thf at 30 c 
 vs ps standards . the structure of 
 terpolymer 1 was 
 assigned to a o network structure with orthorhombic lattice 
 and lattice parameters of a = 33.9 nm , b = 49.4 nm , and c = 82.1 nm ( vide infra ) . film structures formed during self - assembly 
 of pi - b - ps - b - ppc triblock terpolymers 
 were characterized 
 using a combination of small - angle x - ray scattering ( saxs ) as well 
 as transmission and scanning electron microscopy ( tem and sem ) . saxs 
 patterns for the polymers from table 1 and 
 analysis can be found in the supporting information ( figure s6s8 ) . selective polymer degradation 
 of one block has been 
 reported for block copolymers containing polyesters , poly(methyl methacrylate ) , 
 polyisoprene , polybutadiene , poly(ethylene oxide ) and polysiloxanes . hillmyer and co - workers reported the synthesis of mesoporous polylactide 
 through selective degradation of polybutadiene with internal olefin 
 metathesis . emrick and co - workers reported 
 orthogonal degradation of disulfide and phosphoester - functionalized 
 polyolefin triblock terpolymers dissolved in solution but did not 
 backfill nor characterize resulting porous solids . hillmyer and co - workers reported orthogonal degradation 
 of abc triblock terpolymer thin films of polyisoprene - block - polystyrene - block - polylactide , where the polyisoprene 
 block was degraded using ozonolysis , and the polylactide block was 
 degraded using sodium hydroxide . however , 
 ozonolysis of the triblock partially degraded the polylactide block 
 in addition to the polyisoprene block , and removal in bulk polymer 
 films was not demonstrated . additionally , hawker and co - workers reported 
 the orthogonal degradation of thin films of a supramolecular complex 
 of poly(ethylene oxide)-trityl - b - poly(styrene - r-4-hydroxystyrene ) and poly(styrene - r-4-vinylpyridine)-b - poly(methyl methacrylate ) . orthogonal degradation was demonstrated by acid cleavage of the 
 trityl ether linkage and uv degradation of the poly(methyl methacrylate ) 
 blocks . in contrast , the pi and ppc blocks of pi - b - ps - b - ppc triblock terpolymers were orthogonally 
 degradable in bulk films . the pi block was degraded using 302 nm uv 
 light , and the ppc block was degraded by soaking the polymer film 
 in a solution of naoh . irradiation of the block copolymers with 302 
 nm uv light in the presence of oxygen resulted in degradation of the 
 pi blocks and cross - linking of the ps blocks with no apparent effects 
 on the ppc blocks as evidenced by gel - permeation chromatography ( gpc , 
 figure 2 ) and h nmr spectroscopy 
 ( supporting figures s9s12 ) . after each subsequent 
 degradation step , in gpc we observed a clear shift of the polymer 
 to lower molar mass ( figure 2a , b ) . orthogonal 
 degradability was demonstrated on pi - b - ps - b - ppc-1 ( o network structure ) and 
 pi - b - ps - b - ppc-3 ( q core shell double gyroid ) using gel permeation chromatography 
 ( gpc , figure 2 ) and scanning electron microscopy 
 ( sem , figure 3 ) . in the experiment leading 
 to gpc traces in figure 2a , the pi block was 
 degraded first , resulting in a shift in the gpc trace to lower molar 
 mass and broadening of the molar mass distribution , especially on 
 the high molar mass side . this broadening is due to weak cross - linking 
 of the ps block still allowing gpc analysis . polymer films retained 
 their network structure after removal of the pi blocks as evidenced 
 by sem ( figure 3a ) . next , the ppc block was 
 degraded using naoh solution ; as a result , we observed a further shift 
 in the broadened gpc trace to lower molar mass . after removal of the 
 pi and ppc blocks ( 51 vol % ) , the periodic network structures 
 were retained as suggested by the sem micrograph in figure 3c . alternatively , in experiments leading to the 
 traces in figure 2b , the ppc block was degraded 
 first , resulting in a shift to lower molar mass and retention of the 
 narrow molar mass distribution . structures were retained after ppc 
 block removal as evidenced by sem ( figure 3b ) . next , the pi block was degraded using uv light resulting in a 
 further shift of the gpc trace to lower molar mass as well as broadening 
 of the molar mass distribution due to weak ps cross - linking ( vide 
 supra ) . the ps domains also retained their original structure after 
 removal of the two end blocks in sequence : ppc first and then pi , 
 as suggested by the sem micrograph in figure 3d . from the sem and gpc data sets , we demonstrated that degradation 
 of the pi and ppc blocks can be performed orthogonally with retention 
 of the original block copolymer structure . orthogonal degradation 
 of pi - b - ps - b - ppc polymer films ( q and o ) as evidenced 
 by gpc . ( a , b ) gpc traces of pi - b - ps - b - ppc-1 polymer films after ( a ) degradation of the pi ( matrix ) blocks 
 followed by degradation of the ppc ( gyroid minority networks ) blocks ; 
 ( b ) degradation of the ppc blocks followed by degradation of the pi 
 blocks . orthogonal degradation of pi - b - ps - b - ppc polymer films ( q and o ) as evidenced 
 by sem micrographs of the corresponding polymer film cross sections 
 after ( a ) degradation of pi blocks only ( pi - b - ps - b - ppc-3 ) ; ( b ) degradation of ppc blocks only ( pi - b - ps - b - ppc-3 ) ; ( c ) degradation of pi blocks 
 followed by degradation of ppc blocks ( pi - b - ps - b - ppc-1 ) ; ( d ) degradation of ppc blocks followed by degradation 
 of the pi blocks ( pi - b - ps - b - ppc-1 ) . the sem micrographs in figure 3 are high - magnification 
 images showing local structure retention after different sequences 
 of pi and ppc block removal . a low - magnification sem micrograph showing 
 mesoporosity over the entire field of view for a film cross - section 
 can be found in the supporting information ( figure s13a ) . furthermore , sem micrographs of film surfaces after 
 removal of the pi and ppc blocks ( figure s13b 
 and s13c , respectively ) demonstrate that the film surfaces 
 were porous after degradation , allowing for diffusion of metal plating 
 solutions into the mesoporous polymer templates ( vide infra ) . we used electroless and seeded growth 
 deposition to backfill au , cu , and ni metal into mesoporous templates 
 produced by orthogonally degrading the pi and ppc blocks of the networked 
 pi - b - ps - b - ppc templates . electroless 
 and seeded growth deposition were used , as they do not require conducting 
 substrates and have been demonstrated to be effective for block copolymer 
 template systems . mesopores from both pi and ppc degradation were presumed 
 to be hydrophilic from a mixture of carboxylic acids and hydroxyl 
 groups formed by pi degradation and from ppc degradation , 
 respectively . electroless deposition of ni metal into gyroidal mesoporous 
 templates has been reported by hashimoto and co - workers , hsueh et al . , and 
 du sart et al . au metal was backfilled 
 using a seeded growth process adapted from work reported by ho and 
 co - workers . sita and co - workers demonstrated 
 cu metal deposition into lamellar block copolymer templates using 
 electroless deposition . tem micrographs 
 of resulting structures after deposition of au , ni , and cu metal separately 
 into the pi and ppc pores from various pi - b - ps - b - ppc terpolymer templates are shown in figure 4 . au , ni , and cu metal appear dark in the tem micrographs , 
 providing contrast in the images . we backfilled the pi matrix pores 
 of pi - b - ps - b - ppc-4 ( q core shell double gyroid ) with au ( figure 4a ) , ni ( figure 4c ) , and cu ( figure 4e ) , demonstrating that three different metals can 
 be deposited into a single template . additionally , for au , we also 
 deposited metal into the gyroid minority ppc pores of the q core  shell double gyroid structure of pi - b - ps - b - ppc-3 ( figure 4b ) , 
 demonstrating that orthogonal degradation can be used to fabricate 
 metal networks with different structures . we backfilled ni metal into 
 the ppc minority network of the o template ( pi - b - ps - b - ppc-1 , figure 4d ) and backfilled cu metal into the pi minority network pores from 
 the q template ( pi - b - ps - b - ppc-2 , figure 4f ) , verifying metal backfilling 
 is not specific to only the q core deposition of au metal into the polymer templates 
 resulted in patchy coverage of areas 1001000 nm in size , depending 
 on distance of the au gyroid from the film surface . patchy deposition 
 of au metal could be the result of the use of sodium borohydride rather 
 than hydrazine as a reducing agent or 
 the result of decomposition of the plating solution . we expect future 
 optimization of the au plating solutions would result in more uniform 
 deposition of au metal throughout the mesoporous template . alternatively , 
 ni and cu metal both resulted in more uniform metal deposition throughout 
 the film . with this work , we demonstrated that three different metals 
 could be deposited into the pi and ppc pores of the various networked 
 templates . sem micrographs of freestanding au and ni networks after 
 removal of the remaining organic material are available in supporting figures s14s16 . tem micrographs 
 of metal deposited into networked porous templates 
 using electroless deposition ( cu , ni ) , and seeded growth deposition 
 ( au ) . ( a ) deposition of au in pi pores ( pi - b - ps - b - ppc-4 ) and ( b ) ppc pores ( pi - b - ps - b - ppc-3 ) . ( c ) deposition of ni metal into pi pores ( pi - b - ps - b - ppc-4 ) and ( d ) ppc pores ( pi - b - ps - b - ppc-1 ) . ( e ) deposition of cu metal 
 into matrix pi pores ( pi - b - ps - b - ppc-4 ) 
 and ( f ) minority network in pi pores ( pi - b - ps - b - ppc-2 ) . as a proof of principle , we demonstrated 
 first steps of the orthogonal 
 deposition of au and cu metal networks into a single polymer template 
 using sequential degradation and backfilling of the resulting mesopores . although seeded growth deposition of au metal was the least uniform 
 throughout the templates , we used au deposition due to the chemical 
 resistance of au metal to acidic and basic conditions as well as other 
 metal precursor solutions . after degradation of the pi block , 
 au metal was deposited into the mesoporous templates of pi - b - ps - b - ppc-4 . following au deposition , the ps block was left behind in the 
 template and was unaffected by the degradation or backfilling process . because of the incomplete backfilling of the 
 pi pores with au , we expected that electroless deposition would deposit 
 cu metal not only into the ppc pores of the structure but rather into 
 any remaining void space not occupied by au , including the remaining 
 matrix pi pores . although the micrograph from figure 5a is consistent with deposition of metal into both the matrix 
 and gyroid minority networks of the structure , such micrographs alone 
 were insufficient to elucidate exactly where each metal was located 
 within the structure . as a first effort along these lines , the ps 
 block was removed using dissolution in thf to leave behind freestanding 
 au and cu metal networks , which were then imaged using sem ( figure 5b ) . while sem micrographs were consistent with both 
 sets of pores being filled , they also did not further elucidate exact 
 metal locations . orthogonal deposition of au and cu metal into pi - b - ps - b - ppc-4 triblock terpolymer templates . ( a ) tem 
 micrograph of au and cu metal networks ; dark regions indicate the 
 presence of metal . ( b ) sem micrograph ( secondary electron detector ) 
 of au and cu metal networks ; ps block was removed using dissolution 
 in thf . therefore , we turned our attention 
 to high - angle annular dark field 
 scanning transmission electron microscopy ( haadf stem ) to distinguish 
 the au and cu networks due to increased contrast between the two metals . in haadf stem imaging , contrast between two materials is proportional 
 to roughly the square of the atomic number , z. haadf 
 stem micrographs of two different projections of the same hybrid imaged 
 in figure 5 are shown in figure 6a , b . the stem micrograph 
 in figure 6a is consistent with the   projection 
 of the q core likewise , 
 the stem micrograph in figure 6b is consistent 
 with the   projection of the q double gyroid structure . bright regions correspond to higher atomic number au networks , while 
 lighter gray regions correspond to cu gyroid networks . figure 6 clearly demonstrates that orthogonally degrading 
 and backfilling the different pore spaces with two different inorganic 
 ( metal ) compounds was successful . this is corroborated by basic stem 
 projection simulations of the   and   projections with au 
 metal in double - gyroid majority network ( matrix pi derived ) pores 
 only ( figure 6c , e ) and cu metal in both gyroid 
 majority and minority network ( pi and ppc derived ) pores ( figure 6d , f ) , which are consistent with the experimental 
 stem micrographs in figure 6a , b . one detail 
 that became evident from analyzing these images is that the gold strut 
 size appears bigger than that of the cu deposits . this may be attributed 
 to distortions of the block copolymer template structure during or 
 after deposition of au . the fact that we saw this only for au and 
 not for cu is consistent with higher surface mobility of au at moderate 
 temperatures , particularly in nanostructures . the stem projection simulations in figure 6c  f were generated to reflect the differences in strut size 
 between au and cu metals . finally , in order to further elucidate the 
 three - dimensional ( 3d ) character of both networked metal deposits , 
 we reconstructed a 3d model of the sample using haadf stem tomography 
 ( figure 7a and 7b ) . the reconstruction clearly shows that both metals , au ( yellow ) and 
 cu ( red ) are network structures . a movie created from the haadf stem 
 tilt series is available in the supporting information . haadf stem micrographs of au and cu metal networks from pi - b - ps - b - ppc-4 terpolymer templates . ( a , b ) 
 haadf stem micrographs of au and cu networks in single template ; bright 
 regions indicate au metal , while gray regions indicate cu metal . ( c  f ) incoherent 
 stem simulations of q double gyroid metal structures . ( c , e ) 
 simulations of projections in ( a , b ) with au metal only in the matrix 
 ( majority ) network pores . ( d , f ) simulations of projections in ( a , b ) 
 with cu metal in both majority network and minority network pores . 3d reconstruction of au and cu metal networks 
 from pi - b - ps - b - ppc-4 terpolymer 
 templates . ( a , b ) 3d reconstruction 
 with haadf stem tomography of au ( yellow isosurface rendering ) and 
 cu ( red volume rendering ) metal networks where red regions indicate 
 cu metal and yellow regions indicate au metal . ( a ) large - area reconstructed 
 region and ( b ) close up of region contained in white box in ( a ) revealing 
 both cu and au networks . in summary , we report the synthesis of 
 a new orthogonally degradable 
 pi - b - ps - b - ppc triblock terpolymer 
 and the deposition of multiple metals into the resulting porous structures 
 using sequential degradation and backfilling . we synthesized the pi - b - ps - b - ppc triblock terpolymers using a 
 combination of anionic and rapid chain - shuttling polymerization and 
 identified regions in the phase space where the triblock terpolymers 
 self - assembled into cocontinuous network morphologies . we orthogonally 
 degraded the pi and ppc blocks of various networked terpolymers to 
 yield ordered mesoporous templates . we deposited au , ni , and cu metal 
 separately into porous networks produced from degradation of the pi 
 and ppc blocks . finally , we sequentially degraded the pi and ppc blocks 
 and backfilled the structure with au and cu metal to show proof - of - principle 
 for the fabrication of three - component polymer  inorganic hybrid 
 materials where the au and cu metals form separate continuous networks . we anticipate the deposition of multiple materials can 
 be expanded to include different combinations of metals , metal oxides , 
 and ceramic materials for a variety of applications including tandem 
 and size - selective catalysis .