Use of Phase Segregated Block Copolymers with Tunable Properties for the Coating of Surfaces and Coated Substrates

Abstract

Use of phase segregated block-copolymer based on repeating structural elements represented by formula I

##STR00001##

wherein PHA represents at least one block based on one or more a-hydroxy acids, PDAS represents a central block based on a dialkylsiloxane, the PDAS block has a weight average molecular weight in the range of from 4000 to 10000, the blocks PHA have a weight average molecular weight in the range of from 2000 to 10 000, the phase segregated block copolymer has a weight average molecular weight of from 40 000 to 120 000 and wherein R is a divalent organic residue for the coating of substrates and coated substrates.

Claims

1. A composition comprising: phase segregated block-copolymers based on repeating structural elements represented by formula I ##STR00010## wherein: PHA represents at least one block based on one or more a-hydroxy acids, PDAS represents a central block based on a dialkylsiloxane, the PDAS block has a weight average molecular weight in the range of from 2000 to 20,000, the blocks PHA have a weight average molecular weight in the range of from 1000 to 20,000, the phase segregated block copolymer has a weight average molecular weight of from 20,000 to 200,000; and wherein R is a divalent organic radical for the coating of a substrate.

2. The composition of claim 1 wherein the α-hydroxy acids are represented by the formula ##STR00011## wherein R is a linear, branched, or cyclic aliphatic group having 1 to 30 carbon atoms, an aryl group comprising 6 to 30 carbon atoms which may comprise a fused ring, or an alkylaryl group having 7 to 40 carbon atoms.

3. The composition of claim 2 wherein the α-hydroxy acid is selected from glycolic acid, lactic acid, malic acid, citric acid, tartaric acid or from products obtained through diazotation of α-amino acids.

4. The composition of claim 3 wherein the α-hydroxy acid is selected from lactic acid or glycolic acid or mixtures thereof.

5. The composition of claim 1 wherein the alkyl dialkylsiloxane is represented by the formula ##STR00012## wherein Alk, which may be the same or different at each occurrence, represents a linear, branched or cyclic alkyl group.

6. The composition of claim 5 wherein Alk is a methyl group.

7. The composition of claim 1 wherein the substrate is selected from floorings, materials used for building elements in construction or furniture.

8. The composition of claim 1 wherein the substrate is a film, foil or shaped article based on paper or paper-like materials or based on synthetic or natural resins.

9. The composition of claim 1 wherein the substrate is selected from the group consisting of plates, food containers, degradable utensils, tableware, and shaped or formed articles made from wood, plastics, textiles, artificial leather or natural leather.

10. The composition of claim 1 wherein the substrate is selected from substrates with metallic surfaces.

11. The composition of claim 1 wherein the substrate is an implant.

12. The composition of claim 1 wherein the substrate is a stent.

13. The composition of claim 1 wherein the substrate is a bulk solid.

14. The composition of claim 1 wherein the substrate is a polymer granulate.

Description

EXAMPLES 1-4

[0112] Pre-dried Poly(dimethylsiloxane), bis(hydroxyalkyl) terminated (Mw˜8500 g/mol, Mn 5600 g/mol, PDI 1.5, purchased from Sigma Aldrich) and lactide (98%, Aldrich) were charged in a clean pre-dried three-neck round-bottom flask (equipped with overhead KPG stirrer, reflux condenser) and dried in vacuo for 1 h. The reactor was flushed with Argon as an inert gas and was connected to Argon balloon during the reaction. Dry toluene (dried by Na in Ar atmosphere) was added as solvent and the reaction mixture was heated to 90° C. (using a silicon oil bath with a magnetic stirrer). Sn(Oct).sub.2 catalyst (1-0.5 mol-% of lactide) dissolved in 5 mL dry toluene was added drop wise and the reaction mixture was stirred for 20 h at 90° C. (after addition of glycolide 15 h more).

[0113] 10-20 mL dry toluene was added for high viscous solutions. The temperature was decreased to 70° C. and 1,6-hexamethylene diisocyanate (HDI), dissolved in 5 mL dry toluene was added drop wised. The mixture was stirred for 2.5 h at 70° C. The temperature was elevated to 90° C. and pre-dried 1,4-Butanediol (BD) chain extender was added. The mixture was stirred for 2 h at 90° C. Oil bath was removed and the mixture was stirred over night at room temperature.

[0114] Work-Up

[0115] The polymer solution was diluted with the reaction solvent if it is too viscous, coagulated in 500 mL cold Ethanol, washed with technical grade Ethanol (3 times, 500 mL) and finally dried under reduced pressure to yield constant weight.

[0116] The details of the experiments are shown in Table 1.

TABLE-US-00001 TABLE 1 PDMS Macro- Lactide or Sn(Oct).sub.2 BD initiator Glycolide Solvent μL μL μL Ex. 1 PSLLU 7.4 g 7.2 g L- 20 mL 323 424 117 1:1 Lactide Toluene Ex. 2 PSLLU 7.4 g 10.8 g L- 30 mL 485 424 117 1:1.5 Lactide Toluene Ex. 3 PSLLU 7.4 g 14.4 g L- 40 mL 646 424 117 1:2 Lactide Toluene Ex. 4 PSLGU 7.4 g 5.76 g L- 20 mL 162 424 117 1:0.8:0.2 Lactide + Toluene 1.16 g 10 mL Glycolide DMAc (after 20 h (by of Glycolide reaction) addition)

[0117] The molecular weight of the starting materials, the intermediate block polymers obtained before addition of the HDI and of the final products products as well as the polydispersity index are given in Table 2 was determined by GPC as described before. As can be seen the PDMS block had a Mw of 8500 g/mol, the PLA block of between 6900 and 9200 g/mol and the final products had molecular weights Mw of from 55900 to 79400 g/mol. A comparative product (Example 4) obtained from PDMS and HDI only (without lactide) had a Mw of 135 000 and a polydispersity index of 1.36.

TABLE-US-00002 TABLE 2 PDMS content PLA content Example Mw PDI mole % mole % 1 intermediate  15.500 1.33  49 49 1 final  79.400 1.55  48 49 2 intermediate  17.700 1.29  41 58 2 final  55.900 1.36  40 59 3 intermediate  17.200 1.08  34 64 3 final  58.600 1.34  33 66 4 intermediate — — — — 4 final 135.470 1.36 100  0

[0118] The products in accordance with the invention showed good thermal stability and mechanical properties and were melt processible.

EXAMPLE 5

[0119] The polymer in accordance with example 1 (comprising 48 mole % of PDMS in the polymer chain) was used to coat palm leaf plates by dip coating with a solution of the polymer in tetrahydrofurane (0.5 g polymer in 1 ml THF) and thereafter the water uptake of the coated materials was determined at 25 and 60° C. over time. The water uptake was 15 wt % after 10 minutes, 35 wt % after 60 minutes and 55 wt % after 120 minutes (values at 60° C. were 20, 45 and 55 wt %). The uncoated reference material showed a water uptake of 30 wt % after 10 minutes, 70 wt % after 60 minutes and 140 wt % after 120 minutes at 25° C. (the respective values at 60° C. were 45 wt %, 100 wt % and 180 wt %).

EXAMPLE 6

[0120] Two films obtained from the polymer of example 1 with a thickness of 0.12 mm were subjected to an oxygen plasma treatment in a controlled oxygen radio frequence energized plasma chamber for 70 seconds and thereafter the films were pressed together to provide bonding after plamsa exposure. Scanning electron microscopy (SEM) images showed the bonding of the sheets.

EXAMPLE 7

[0121] Canvas textile (100% cotton) was dip coated with a solution of the polymer of example 1 (0.5 g/ml in THF). After 2 minutes of drying time, the water contact angle was determined. The coated material showed a strong increase in static water contact angle compared to polylactic acid used as comparison which is an indicator of the hydrophobic nature of the coating.

[0122] Similar results were obtained when natural leather was coated with the coating composition (1 g/ml in THF) of the same polymer (drying time in this case was 3 minutes).