different numbers of arms and chain lengths are necessary for a better understanding of the

influence of the dendrimer-like structure.

 3.4 Experimental Methods

3.4.1 Materials

 The synthesis of the PS-b-PtBA (Dendl, 2s = 240,000 g/mol, PDI = 1.26) and PS-b-PAA

(Dend2, 2s = 139,000 g/mol, PDI = 1.28) dendrimer-like copolymers was realized according to

a previously reported procedure.100 These block copolymers consist of an eight-arm PS core (2\%,

= 10,000 g/mol, ~ 12 styrene units/arm) with a sixteen-arm PtBA (2, = 230,000 g/mol, ~ 112

tert-butylacrylate units/arm, PS wt % ~ 4 %) or PAA (2, = 129,000 g/mol, ~ 112 acrylic acid

units/arm, PS wt % ~ 7%) corona. The PAA homopolymer (PAA250K, 2Ms ~ 250,000 g/mol) was

purchased from Aldrich Chemical Co. and was used as received without further purification.

3.4.2 Langmuir Films

 Surface pressure measurements were accomplished by use of a Teflon Langmuir trough

system (W= 160 mm, L = 650 mm, KSV Ltd., Finland) equipped with two moving barriers and a

Wilhelmy plate. The PS-b-PtBA dendrimer-like copolymer sample (Dendl) was prepared by

dissolving approximately 1 mg of polymer in 1 mL of chloroform. The PS-b-PAA dendrimer-

like copolymer (Dend2) and the PAA homopolymer (PAA250K) Samples were prepared by

dissolving approximately 1 mg of polymer in 1 mL of a chloroform/ethanol mixture (1/2 in

volume). Volumes ranging from 10 to 30 puL were spread dropwise with a gastight Hamilton

syringe on Millipore filtered water (subphase resistivity > 18.2 MGZ.cm) of the desired pH value,

and the spreading solvents were allowed to evaporate for 30 min. In all the experiments,

subphase temperature and barrier speed were kept constant at 25 OC and 5 mm/min, respectively.