PMID- 31134980
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20191120
IS  - 1463-9084 (Electronic)
IS  - 1463-9076 (Linking)
VI  - 21
IP  - 22
DP  - 2019 Jun 5
TI  - Evidence of pre-micellar aggregates in aqueous solution of amphiphilic PDMS-PEO 
      block copolymer.
PG  - 11983-11991
LID - 10.1039/c9cp02195g [doi]
AB  - The self-assembly process in a water solution of an amphiphilic 
      polydimethylsiloxane-b-polyethyleneoxide (PDMS-PEO) diblock copolymer was 
      investigated by means of small-angle X-ray scattering (SAXS) experiments in the 
      concentration region below (and near) the critical micellar concentration (c.m.c. 
      = 0.007 g cm-3). In the highly diluted region, at the copolymer concentration of 
      c = 0.002 g cm-3, the early stage of the self-assembly process was characterized 
      by the formation of small (primary) micellar units (with a radius of R = 2.7 nm) 
      with core-shell morphology, which coexisted with larger supramolecular aggregates 
      of entangled micelles (with an average radius of R = 9.5 nm). The increase in the 
      copolymer concentration (to c = 0.005 and c = 0.01 g cm-3) caused increase in the 
      sizes of both the small micelles and supra-micellar aggregates. Interestingly, at 
      the concentration of c = 0.005 g cm-3, both the size and micelle aggregation 
      number (Nagg) were found to increase on increasing the temperature in the range 
      of 10 </= T </= 55  degrees C. This phenomenon was characterised by the dehydration process 
      of the ethylene oxide (EO) segments, as evidenced by the calculation of excess 
      water in the hydrophilic shell of the micelles. The more compact (less hydrated) 
      structure of the hydrophilic PEO chains, which strongly influenced the 
      spontaneous curvature of the amphiphile hydrophilic region, turned out to be the 
      driving factor that favoured the increase in the micelle aggregation number with 
      the increase in temperature. The obtained results evidence that the self-assembly 
      process of PDMS-PEO copolymer amphiphiles is a gradual process that is already 
      present at the very low concentration region (far below the macroscopically 
      determined c.m.c.); moreover, it is characterised by a multi-stage organization 
      process, where the primary building blocks self-assemble into more complex 
      secondary structures that encompass multiple length scales.
FAU - Lombardo, Domenico
AU  - Lombardo D
AD  - CNR-IPCF, Istituto per i Processi Chimico Fisici - (Sez. Messina) Viale, F. 
      Stagno D'Alcontres, 37, I-98158, Messina, Italy. lombardo@ipcf.cnr.it.
FAU - Munao, Gianmarco
AU  - Munao G
FAU - Calandra, Pietro
AU  - Calandra P
FAU - Pasqua, Luigi
AU  - Pasqua L
FAU - Caccamo, Maria Teresa
AU  - Caccamo MT
LA  - eng
PT  - Journal Article
PL  - England
TA  - Phys Chem Chem Phys
JT  - Physical chemistry chemical physics : PCCP
JID - 100888160
EDAT- 2019/05/29 06:00
MHDA- 2019/05/29 06:01
CRDT- 2019/05/29 06:00
PHST- 2019/05/29 06:00 [pubmed]
PHST- 2019/05/29 06:01 [medline]
PHST- 2019/05/29 06:00 [entrez]
AID - 10.1039/c9cp02195g [doi]
PST - ppublish
SO  - Phys Chem Chem Phys. 2019 Jun 5;21(22):11983-11991. doi: 10.1039/c9cp02195g.