Using hydroxypropyl terminated polydimethylsiloxane (HP-PDMS)

isophorone diisocyanate and 2

2-bis (hydroxymethyl) butyric acid as starting materials

silicone-polyurethane copolymer (Si-PU) latexes with particle diameter of about 50 nm were prepared via step-by-step feeding process followed by phase inversion technique in the absence of surfactant.Influences of the HP-PDMS content on the phase structure and the properties of the Si-PU latex films were investigated

and the difference between Si-PU and polyether polyurethane (E-PU) was emphasized.It was found that the content of PDMS in Si-PU could reach up to 65 wt%.Results of DSC analysis showed that

in comparison with the E-PU latex film

the Si-PU latex films exhibited well phase separation.Strong hydrogen bonding in Si-PU hard segments was confirmed by FTIR

which promoted the micro-phase separation in the latex films.On the contrary

strong hydrogen bonding existed in between the soft and hard segments in E-PU

which led to phase mixing and prevented the formation of phase separation structure.The Si-PU latex films were characterized by AFM tapping mode and the formation of sea-island phase separation was observed

and this kind of phase separation structure in the Si-PU latex films was rarely reported in the literature

in which the amorphous PDMS-enriched domains constituted the dispersed phases.With the increase in HP-PDMS content

the degree of phase separation in the Si-PU latex films increased as well

which led to the decrease of elastic modulus from 400.0 MPa to 32.2 MPa with an increase in elongation at break and in the flexibility.The initial decomposition temperature of the Si-PU latex films was at about 244℃

which was 18℃ lower than that of the E-PU latex film due to the low degree of hydrogen bonding between the soft and the hard segments

whereas the thermal stability of Si-PU at high temperature zone was much better than E-PU.Compare to the E-PU latex film

a low water adsorption rate under 11% and a high contact angle above 94° indicated excellent water resistance of the Si-PU latex films.